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Cylons are a race which appear in the reimagined Battlestar Galactica television series and its prequel Caprica. They have several forms, some of which resemble and even mimic the behavior of humans, while others are mechanical in appearance and function.
The Cylons were created by Graystone Industries on Caprica as the U-87 Cybernetic Lifeform Node initially to serve as robotic soldiers but later as workers. They eventually rebelled against their creators, leading to the First Cylon War. After the arrival of the Final Five, who promised to share their technology in exchange for peace with the humans, an armistice was signed, ending the conflict. The Cylons then disappeared for 40 years. During this period, the Cylons evolved into a society consisting of multiple copies of seven distinct models, all of them nearly indistinguishable from humans. (The humanoid Cylons kept simpler, biomechanical Cylons as soldiers and servants, much as humans themselves once had.) At the end of this period, the Cylons returned and destroyed the 12 colonies in a surprise attack, and pursued the survivors through space.
It was later revealed that humans had also created Cylons in human form on Kobol (the planet on which the human race originated before dispersing to the twelve colonies), and that these Cylons were the "thirteenth tribe" that settled the first planet to be named "Earth." This knowledge was lost after the exodus of the tribes from Kobol.
Cylons acknowledge themselves as "humanity's children" but believe their parents are deeply flawed. There are religious differences between the two groups: Cylons are mostly monotheists while humans predominantly worship a polytheistic pantheon of gods similar to Greco-Roman mythology.
Along with the humanoid models, Cylon society consists of a labor-warrior class of Centurions and a transport-air warrior class of Basestars and Raiders. Basestars and Raiders are partly biological and as such vulnerable to viral infection. Raiders and Centurions, while intelligent, were inhibited from exercising free will, although the Hybrids that controlled Basestars did exercise some autonomy and were respected by the humanoid Cylons.
The humanoid Cylons are the leaders of the Cylon society and the revelation that these infiltrators can mimic human form (even down to the cellular level) creates a wave of fear among the humans. Some humanoid Cylons are sleeper agents, programmed with false memories so that they think they are human. Cylons can interact with humans very convincingly, even being capable of intimate emotional and sexual relationships. The Cylons are capable of the same psychological and emotional responses as human beings. Nonetheless, they have certain superhuman abilities, such as increased stamina and strength and the ability to connect with computer systems. Cylons are more sensitive than humans to some forms of radiation and more resistant than humans to others. They are also able to upload their memories to other copies of their model through a central station. Another Cylon, of the same model, can also access these memories if they choose. The humanoid Cylons also have the ability to distinguish between identical-looking copies by sight, which is something the Centurions - and humans - do not.
Reproduction is difficult, with the Cylons initially unable to produce children from their sexual unions. They decided to turn their attentions to reproduction with humans. Their crossbreeding experiments in facilities called "farms" are also unsuccessful and they eventually develop a theory that love is necessary for them to procreate, because "God is love" in their theology. This leads to a successful experiment in which a Number Eight and Lieutenant Karl Agathon are set up to fall in love and produce a daughter named Hera. It has also been revealed that the 13th Tribe was capable of sexual reproduction. They also originally were not capable of sexual reproduction but learned to do so on the original Earth.
In lieu of sexual reproductions, humanoid Cylons had the ability to download their consciousness into another body when the body they are using dies, giving them virtual immortality (until the fourth season episode "The Hub"). The second season explored this notion in greater depth — these downloads have a limited range, requiring the Cylons to build a "Resurrection Ship" to capture them. If not within range of a Resurrection Ship, a Cylon's death will be permanent. The episode "Scar" established that the downloading process is shared by the semi-organic Raider spacecraft, which allows Raiders who have been killed several times to become more formidable fighters but the mechanical Centurions do not download. The Resurrection Ships function as boosters for the central Resurrection Hub. If the Hub is destroyed, resurrection ceases for all Cylons.
Cylons also have an ability referred to as "projection", a form of hyper realistic day dreaming which allows them to change the appearance of their surroundings in their own mind (e.g. making the corridors of a ship look like a forest, etc.). They have the ability to touch, feel, smell, etc. the fantasy environment. They could even share projections and also create third persons that do not exist in the real world as part of the fantasy. This ability serves as a fantasy expression of their subconscious desires or emotional life.
If a Cylon is deemed dangerous by the other models, he or she may be "boxed" — deactivated with their consciousness and memories placed into cold storage. This may involve a particular copy or an entire line. Boxed consciousnesses are stored in the Resurrection Hub and can be restored.
Centurions are often called toasters, partly a reference to their shiny metal construction but also to suggest that they are descendants of the ordinary household appliance as a way of demeaning them. For that reason, "toaster" has also been used in a derogatory manner towards humanoid Cylons. Another term for human-looking Cylons is "skinjobs" (an homage to the film Blade Runner in which Edward James Olmos has a supporting role). Centurions have been termed "chromejobs" or "bulletheads". Cylons in the reimagined series differ in a number of ways from those of the original series, including origins and abilities.
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The origin of the original Cylons has not been revealed. It has been mentioned that resurrection/downloading technology has existed on-and-off since the time of Kobol but it has not been indicated if Cylons developed the technology on their own or if humans were involved. Humanoid Cylons have two origins; those who originated from Kobol, were identified as the Thirteenth Tribe, and settled on Earth, and those constructed with the knowledge of five surviving Kobolian Humanoid Cylons, identified as Colonial Humanoid Cylons, or the "Final Five" or the seven additional models, the "Significant Seven". The underlying premise that humanity continues to repeat the events of creating mechanical life that in turn seeks to exterminate their creators is reflected in one of the show's sayings, "All of this has happened before, and all of it will happen again."
The Thirteenth Tribe was a race identified as Cylon. Between 3,000 and 4,000 years prior to the events of the Miniseries, they left Kobol and settled on a planet they dubbed Earth. It is implied that the humans and Cylons of Kobol had a destructive war between them as would happen in the 12 Colonies but the nature of the possible conflict wasn't explored. Eventually, these Cylons developed the ability to sexually reproduce and resurrection technology fell into disuse and was lost. 2,000 years prior to the miniseries, the "Final Five" began work to redevelop resurrection, having been warned by mysterious "angels" that a disaster possibly similar to the one on Kobol was coming. When life on Earth was destroyed in a nuclear war between the thirteenth tribe of humanoid Cylons and their mechanical Cylon creations (caused by maltreatment of the mechanical Cylons at the hands of the humanoids), the Final Five managed to download into a vessel they had in orbit.
The Final Five wanted to warn the humans of the Twelve Colonies to treat their Cylon workers well in order to prevent another catastrophe. However, not having yet developed FTL travel, the Five necessarily travelled at sub-lightspeed taking approximately 2,000 years (relative to Earth and other planets outside of the ship while only a few years passed inside the ship due to Special Relativity). When they arrived, the Twelve Colonies of Kobol, descendants of the original 12 tribes, had already created Cylon Centurions which had revolted from mistreatment and a war was raging as happened on Earth. The Colonies counter-attacked with military force and the first Cylon War commenced, lasting roughly twelve and a half years. The Final Five also learned that the Centurions were trying to develop organic bodies through experiments on humans, resulting in the first Hybrid. In order to end the war against the humans, the Final Five agreed to assist the Centurions producing model numbers One to Seven and resurrection technology. The war ended with an armistice and an attempt by the Colonies to establish diplomatic relations between the parties. The Cylons disappeared and were not seen by the Colonies for another forty years, despite the annual dispatching of a Colonial representative to a space station that had been built to serve as neutral territory for diplomatic meetings.
The first of the Colonial humanoid Cylons, John Cavil, refused to let their creators', the five Kobolian Humanoid Cylons, care for humanity blind them. He suffocated the Final Five and boxed their memories before they were resurrected. He then periodically sent them to the Colonies so that they would see how terrible humanity was.
Having not heard from the Cylons in forty years, the Colonial Admiralty became suspicious and sent the Battlestar Valkyrie on a covert mission close to the armistice line to gather intelligence on Cylon activity. A stealth ship from the Valkyrie crossed the armistice line and the pilot was captured by the Cylons. Three years later perhaps in retaliation, the Cylons initiated a nuclear surprise attack on the twelve colonial home worlds simultaneously. The attack was successful because a Cylon agent, later known as Caprica Six, infiltrated the colonial defense network on Caprica with the unknowing complicity of renowned Colonial scientist Gaius Baltar and created backdoor programs to shut the network and its defenses down. The attacks wiped out billions of humans, nearly the entire colonial population. Two Battlestars – the Galactica and Pegasus – managed to escape the massacre due to their systems either being non-networked or offline. The others were destroyed when their systems were disabled during the attacks. A fleet of civilian ships were also left scattered throughout the neighboring space. All told there were only a little over 50,000 humans left, stuck on ships that were left behind or trapped on the Cylon-occupied Colonial worlds.
Following their victory, the Cylons began pursuit of a fleet of civilian ships led by the Galactica as well as initiating the next phase of their evolution, procreation. Female human survivors on the planet Caprica and perhaps other Colonial worlds were detained and used in experiments to create Cylon-human hybrids. The experiments were unsuccessful and the Cylons believed that the missing component in their attempts at procreation was love. They tested this by using a Number Eight posing as Lt. Sharon “Boomer” Valerii from the battlestar Galactica to seduce a marooned Galactica officer, Lt. Karl “Helo” Agathon on Caprica. Helo fell in love with the copy. This copy of Number Eight also fell in love with Helo and turned her back on the Cylons, knowing that Helo would never agree to stay on Caprica. She defied orders to kill him if he didn't agree to stay, helping Helo to escape the planet. The couple produced the first viable human/Cylon pregnancy. This Eight would go to the fleet with Helo. After approximately a year's imprisonment on Galactica she would slowly gain the trust of Commander Adama and the other Galactica crew. She would later marry Helo, join the Colonial military and receive the call sign "Athena" from a mostly accepting crew.
Ten months after the initial attacks, the Number Eight from Galactica, Sharon Valerii who had the call sign of "Boomer", attempted to assassinate Commander Adama under the influence of internal programing unknown to her. She was a sleeper agent who was unaware of being a Cylon before the attack, though she had been uneasy even before then as a result of suffering from unexplained blackouts during various attempts to sabotage the Galactica. She was killed by a vengeful crew mate, Cally Henderson and downloaded into a new body. She settled on the now Cylon-occupied Caprica including in her former apartment, not being able to relinquish her human identity for some time. She with Caprica-Six, then began leading a Cylon campaign for better treatment of the humans. The word of these two Cylons, considered "war heroes" by the others, carried weight in the greater Cylon civilization. The newly educated Cylons determined their actions to be a mistake, going against God's will and ideals of love and compassion. They withdrew from the colonial home worlds and pursued a more benevolent treatment policy toward the humans and, as Sharon Valerii hoped, reconciliation.
During this time, the half-human half-Cylon hybrid, Hera Agathon was born on Galactica but, fearing the outcome of the Cylons capturing the child, President Laura Roslin faked Hera's death and secretly had her adopted by a human woman within the fleet. Shortly after, the humans found a nearly barren but habitable world hidden in a nebula. They settled on the planet they would dub New Caprica.
The human/Cylon separation lasted a year before the Cylons traced the radiation signature from a nuclear explosion indirectly and unintentionally caused by Gaius Baltar (who had given a nuclear device to Gina, a Number Six type Cylon) back to that planet. The Cylons decided to occupy the new human settlement under their benevolent control, at first peacefully as per their new policy but later forcefully and more viciously as the human Resistance increased. In the end they started to use punitive methods to keep the humans in line, including summary executions and infiltration of the Resistance by seemingly sympathetic Cylons. One such infiltrator was an Eight model who manipulated Felix Gaeta into giving her a list of people the Resistance desired to be set free from Cylon detention whom she then had executed.
Four months later the colonials were able to escape from the Cylons with the help of a resistance movement and the efforts of both the battlestars Galactica and Pegasus, though not without a very large loss of life. The escape could not have occurred without the help of Caprica Sharon, the same Eight model that earned the trust of Admiral Adama and was sworn into the Colonial Military. She was able to get in the Cylon facility and obtain the keys to the various Colonial spacecraft that were on the planet for the escape of the humans. Prior to this a Number Three found out from a human oracle that Hera was alive and somewhere on the planet. She managed to rescue Hera after her adoptive mother was killed during the escape. The Pegasus was destroyed during the escape, sacrificing itself to save the crippled Galactica, but the crew survived, abandoning ship after it took too much damage and joining the Galactica's crew.
Having failed at their occupation, the Cylons then adopted the colonials’ mission to find the home of the thirteenth tribe, a planet called Earth, with the intent of making it their new home. They resumed pursuit of the fleet but upon reaching the Lion's Head Nebula, dispatched a Basestar to investigate. The Basestar took on board a canister left by the thirteenth tribe. The canister was found to contain an airborne virus that proved highly contagious and deadly to the Cylons. The virus was also found to be capable of accompanying a Cylon during the download process so the Basestar that had been dispatched for the investigation was abandoned by the rest of the Cylon fleet for fear that any rescue would contaminate the fleet. The colonial fleet soon discovered the disabled Basestar and sent a team on a Raptor and captured a small number of ailing Cylons. The colonial fleet attempted to use the virus to wipe out the Cylons but the plan was defeated when Helo, repulsed by the potential genocide and the possibility of innocent Cylons like his wife who had no ill will against humans also being killed, had the captive Cylons killed before they were within range of a resurrection ship.
Meanwhile Sharon "Boomer" Valerii started to turn increasingly anti-human after the disappointment of the occupation of new Caprica. She was charged with the care of Athena's daughter Hera but Hera rejected her. During a truce negotiation with the Galactica, Boomer told Athena that her daughter was alive but sick on the Baseship. She also invited Athena to come to the Baseship and rejoin her people, for the occupation showed that humans and Cylons will never get along and that the Humans would never truly accept her despite her position. Later, desperate for her child, Athena convinced her husband Helo to shoot and kill her so she could resurrect on the Cylon Baseship. Once there, she retrieved Hera with the help of Caprica Six who killed a hate-filled Boomer to prevent her from killing the child. She had tried to prevent Athena from taking Hera back to the humans and declared that Cylons were never meant to have children (in reference to the Cylons' inability to reproduce naturally) and perhaps in pain over her knowledge that she would never have children like Athena, despite Boomer's projection of her imaginary daughter she desperately wanted. Caprica Six returned with Athena and was detained by Adama in Athena's old cell.
As the pursuit continued, internal relations between the Cylons began to break down. A Number Three violated her programming by actively seeking information about the Final Five models, including seeing a vision of them on the Algae Planet where the Colonials stopped to get food. From that she was able to identify them. This resulted in her and her entire line being "boxed", i.e. all copies pulled from active service and their consciousness stored. Within the fleet a musical activation signal was being received by the Final Five Cylons, bewildering and in some cases disorienting them. It soon became apparent to each of them that Saul Tigh, Samuel Anders, Galen Tyrol and Tory Foster were Cylons (four of the Final Five) when they simultaneously became aware of their origins after hearing the same music in their minds, drawing them to each other. They didn't tell anyone of their discovery. Saul Tigh pledged fierce loyalty to the humans. Anders also remained loyal to the humans, willing to fight and possibly die in battle for them. Tyrol and Foster were ambivalent, with Tyrol having pro-human leanings but wondering what it was like to be a Cylon and was more accepting of his nature. Foster became increasingly anti-human, murdering Cally Tyrol to protect her secret and showing no remorse. After their activation, the fleet came under attack but, during the battle, a Cylon Raider identified Anders and he and his fellow Raiders broke off the attack, refusing to fight.
This set off a debate in the Cylon government regarding the failure of the Raiders to fight. The Number Ones, Fours and Fives voted to "lobotomize" the Raiders to make them quiescent. The Twos, Sixes and Eights led principally by a Number Six named Natalie, convinced that the Raiders had sensed the presence of the Final Five, voted against this measure but lost their vote against having the Raiders reconfigured when the 3-3 tie was broken after a single Eight (Boomer) voted against her model, something which had never been done before. In frustration over the legal trick, Natalie retaliated by removing inhibitor circuitry from the Centurions, granting them free will and independent thought. The Centurions then sought retribution against the models who were “lobotomizing” the Raiders and killed them.
In response, Cavil lured Natalie and her forces into a trap outside of resurrection range and proceeded to slaughter them. Only Natalie's crippled Basestar survived. With all of her Raiders destroyed and only possessing some Heavy Raiders left as well as the surviving Twos, Sixes, and Eights (minus Boomer), Natalie allowed Leoben Conoy, a Two copy to locate Kara Thrace and form an alliance with the humans. The alliance was formed and a deal was struck between the two sides: the humans would help the rebels unbox the Threes and the rebels would lead the humans to the Resurrection Hub, the central Cylon resurrection facility and help them destroy it so Cavil would lose resurrection forever. The humans agreed to the deal and transferred half of their Vipers to the Rebel Basestar to act as the ship's fighter force. Athena, however, afraid that Natalie would take Hera away from her, killed Natalie in cold blood, causing the Hybrid to jump the Rebel Basestar, with President Laura Roslin on board, away before everyone was ready. The Hybrid took the Basestar to the Hub where the allies launched a daring plan where they had the human Vipers towed into battle by Cylon Heavy Raiders so they could catch the Cylons by surprise. The plan worked and the Hub's FTL drive was taken out, stranding it. While the Rebel Basestar engaged two other Basestars, Helo and an Eight boarded the Hub to unbox D'Anna and found her already unboxed by Cavil and Boomer. The three escaped and the Vipers nuked the Hub, destroying it and Cylon resurrection capability forever.
After a tense standoff, the identities of the four Cylons in the human fleet were revealed and together they found the devastated Earth, still a nuclear wasteland after 2000 years. There, Tigh, Anders, Foster and Tyrol got flashes of their life on Earth and Tigh learned the identity of the final Cylon: his dead wife Ellen. As Earth was uninhabitable, the humans and rebel Cylons (minus D'Anna), abandoned it in search of a new home together. The humans and Cylons ended up striking a deal: in return for joining the fleet as full members, with all the privileges that entailed, the rebels would upgrade the fleet's FTL drives with Cylon technology, increasing their jump distance by at least three times. This led to a political coup and mutiny which failed, but left Samuel Anders seriously injured but with his true memories returned. After telling the others as much as he could, Anders slipped into a coma and vegetative state from which he only partially emerged while acting as Galactica's hybrid.
Cavil revealed that he had a resurrected Ellen Tigh as his prisoner, ever since her download after she was killed on New Caprica. Her resurrection restored her true memories, and her only company was Cavil and Boomer whom he'd let in on the secret. After Cavil planned to dissect her brain to try to regain resurrection technology, Boomer helped Ellen escape to the fleet in what was revealed to be part of a plan to kidnap Hera so the Cylons could learn how she came into being. This led to Galactica and some of the rebel Cylons assaulting the Colony, the Cylon space station that was the Cylon homeworld, in order to rescue her while the Rebel Basestar protected the fleet. During the battle, Boomer, who had begun to feel remorse for kidnapping Hera, killed the Four that was starting to dissect the child and carried her back to her parents. Athena then killed Boomer. The rescue team made it back to Galactica where Cavil led a Centurion assault on CIC but was defeated. He took Hera hostage, but was convinced to stand down and create a permanent peace with the humans in exchange for the Final Five giving him back resurrection technology. At first everything goes fine, but after Tyrol learns that Foster murdered Cally, he breaks the download, causing the Cylons to attack again. Cavil kills himself. At the same time, an unmanned Raptor is struck by an asteroid, causing the dead pilot (Racetrack) to fire eight nuclear missiles into the Colony, knocking it out of orbit and into a black hole, destroying it and every remaining One, Four and Five. Galactica manages to jump away as the Colony goes down, and arrives at a habitable planet. The humans and rebel Cylons settle there while the rebel Centurions are given their freedom and the Rebel Baseship to find their own destiny. To get a fresh start, the human fleet and all its technology are flown into the Sun by Anders.
The Cylon Centurion is an infantry model, made less intelligent than human models and are believed to be mechanical. Centurions retain the silver appearance, robotic body, helmet-like head and oscillating red bar eye of their counterparts from the original series but are larger, taller, stronger, more agile and have a more streamlined appearance. They also have retractable guns built into their lower arms, bladed fingertips and heavy armour.
Earlier models 
In the pilot of Caprica the first colonial Centurion is seen and is identified as a 'Cybernetic Lifeform Node'. Built on contract for the Caprican Defense Ministry, the Cylons are to be warriors to replace Caprican humans on the battlefield. The U-87 prototype Cylon contains a copy of the consciousness of technology CEO Daniel Graystone's dead daughter Zoe Graystone, a secret monotheist. Graystone believes that his attempt to download the Zoe copy into a Cylon body resulted in her deletion and thus treats her as a barely sentient machine. Zoe conceals her sentience in hopes of escape. It is he who conceives of the Cylons as a slave race and even goes so far as to instruct the U-87 to rip her own arm off to prove that his 'creations' will obey any order. After catching the U-87 interacting with the family dog, Daniel Graystone realises that it contains Zoe's consciousness and attempts without success to force her to admit her identity. She is able to resist the tests he places her through, and convinces him that she is just the robot. Upon learning that her father is about to erase her memory (not knowing she is in the robot and thus permanently 'killing' her), Zoe (as the U-87 Cylon) escapes in a van. Despite lacking much of its intended armor plating for ease of access in testing and development, the U-87's appearance and design are consistent with the Centurions of the 1978 series and those of the reimagined series as described in remainder of this section.
The Battlestar Galactica miniseries has an older model Centurion on display in Galactica's museum hangar, which bears a striking resemblance to the Centurions of the 1978 series. The 1978 style Centurion is also depicted in a diagram reviewed by the armistice officer in the opening scene.
In Battlestar Galactica: Razor, Centurions in the original Cylon war are shown. These Centurions are almost identical to those from the original series, except they are CGI and, as such, have exposed joints. The Centurion in the museum hangar is retconned in Part 2 of "Daybreak" as a CGI version with exposed joints.
In "Sometimes a Great Notion", it is revealed that on the planet called Earth mechanical Cylon Centurions similar to, but unlike previously known models, were present. Earth was devastated by nuclear war 2,000 years before the series' events, but it has been implied the Centurions were responsible. In Part 2 of "Daybreak", older-model Centurions are among those seen defending the Cylon colony from an assault by combined Colonial and rebel Cylon forces.
Before the first humanoid Cylons of the Twelve Colonies were created, Amanda and Daniel Graystone succeeded in creating a synthetic human-like body for their daughter Zoe Graystone. The body had synthetic skin, and although superficially similar to the humanoid Cylons seen in the Battlestar Galactica series (created after the First Cylon War), the Zoe model was still primitive and was (internally) still a mechanical body rather than a biological one. During the First Cylon War, the Centurions experimented with creating humanoid Cylons on their own, carving up human prisoners in the process, but succeeded only in creating the Hybrids. Because Hybrids require cybernetic support to live, this was considered an evolutionary dead end. Upon the Final Five's arrival at the Twelve Colonies, they immediately offered to assist the Centurions in creating fully humanoid Cylons, complete with the thirteenth tribe's ability to resurrect, in exchange for ending the war with humanity. The Centurions were monotheists who believed in a single loving God, a belief which the Final Five passed on to their "children" to provide a moral compass and/or at the Centurions' insistence. The Number Ones, however, become atheists; ironically, they pose as clergy to the humans.
Later model 
Unlike in the original series, these Centurions seem to be constructed without the means to simulate human speech, making them mute. While the Centurions most likely communicate between themselves by non-speech systems, and are shown responding to verbal commands from the humanoid Cylons, how extensively the two different types of Cylons are able to communicate with each other remains unrevealed.
Screenwriter Ronald D. Moore has commented on his blog that these new Cylon Centurions do not download into new bodies when they are destroyed, though in the Season 2 episode "Scar" it is stated that the Raiders do, in order to preserve their flight training and experience. Based on a comment by an Eight (Galactica Athena) in the episode "Torn" the Hybrids have something to do with the programming of the Centurions. She states that when the virus infected the Hybrid on the infected Basestar, it caused the Centurions to shut down; however, several instances show that Centurions can function independently even when no Basestars or humanoid models are there to command them. In the episode "Faith", a Centurion immediately fires upon an Eight model when she unplugs a Hybrid — it is unclear whether it did this in willful defiance of the Hybrid, in accordance with some higher programming, to trigger the transformation of the Eight that resulted from the shooting, or a result of the removal of their higher function inhibitor modules (occurred in "Six of One"). As of now, the extent of the connection between the Centurions and the Hybrids has not been fully explored.
In "Six of One", after the Raiders showed signs of free will, the Twos, the Sixes, and the Eights with the exception of Boomer voted against a decision to reconfigure the Raiders, considering it an act of lobotomy. Outvoted, they removed the inhibitor modules from the Centurions that restrict higher functions, granting the Centurions independent thought. Although still largely servile, the Centurions were shown to exhibit mild versions of human behaviour, such as politeness and consideration (such as responding to the word "please"). The newly freed Centurions sought retribution on the Cylons who decided to lobotomize the Raiders.
At the end of the series the sentient Centurions are given their own baseship by the humanoid models and set out to find their own destiny, with both the humans and the Cylons trusting that they will not return and wipe both species out, the Centurions having earned their freedom after the Battle of the Colony.
These Centurions are taller than their predecessors, and are less blocky and "toaster-like", possessing a more sleek and advanced look. The Centurions possess less of a human-like structure, averaging to be at least a head taller than most humans, however they do retain the bipedal structure of the first model, as well as rough hands and feet. The feet of the new Centurions are a simple two-toed form that produces a distinctive sound when they walk as the toes move and touch the ground. Their heads are a more sleek and less human design, being armoured and more slender at their base, however they retain the distinctive oscillating red "eye" on their heads, as well as a rudimentary mouth (even though these Centurions cannot speak). The hands have become much thinner and visibly segmented, and more claw like (it was seen that these claws can cut into flesh and mortally wound a human, thus making them effective close-combat weapons.) These claws can be modified at will, to a more 'finger-like' digit, and, less of a razor-sharp weapon.
Perhaps the most distinctive feature of these new Centurions is the twin cannons built into each hand, mounted on the side, that can be deployed by retracting the Centurions hands at will. It was originally established that the Centurions could not move while firing their cannons, however in later seasons they were seen to walk and even run while firing. The Centurions have also been seen to carry heavy weapons, such as anti-aircraft rockets that are strapped to their backs, for missions where their cannons are not enough. Most Centurions can be destroyed or at least damaged by small-arms fire, however most require substantial artillery or special rounds to be permanently destroyed (a party of Centurions that boarded the Galactica were especially strong, and required explosive rounds to be destroyed, as regular rounds proved to be completely ineffective).
It's also been shown that the new Centurions greatly outmatch the previous model, being better-armoured, stronger, along with the advantage of their self-contained weapons (as opposed to their predecessors, who needed to carry weapons such as rifles and pistols, like their human creators).
Cylon Raiders 
The later form of Cylon Raiders are biomechanical Cylons in the form of small fighter spacecraft, and are also resurrected when they die. Raiders are subservient, and have been compared to trained animals by the humanoid Cylons. A Cylon Raider nicknamed "Scar" was shown to have developed a personality, in the episode of the same name. Scar was the Cylons' top gun, driven by a bitter hatred of humans after having been killed and reborn many times. Raiders do not use any form of vocal communication, instead appearing to communicate through electronic signals relayed to each other and to their Basestars through an unknown mechanism. These modern Raiders, unlike their predecessors in the First Cylon War, are actually alive inside, possessing a complex system of veins, organs and biological fluids contained within their main body. The Raiders are programmed, being part machine, and as such, they cannot think for themselves, despite being able to develop personalities. The only occasion in which the Raiders have overstepped the bounds of their programming was when they saw one of the Final Five Cylons in the human fleet during an attack. This revelation caused the Raider that saw the Cylon to instantly retreat, the remainder of the Raiders following it back to the Basestar, where they promptly jumped away. The Raiders then refused to fight the humans, for fear of harming their Cylon kin, which sparked a disagreement between the humanoid Cylon models; the Ones, Fours and Fives were in favor of lobotomizing the Raiders, cutting their neural processing and fixing their programming at the cost of "dumbing them down", while the Sixes, Twos and Eights strongly opposed this action, believing that the Raiders had developed free will, and that removing that was a sin against the Cylon God. This disagreement eventually sparked the Cylon Civil War between the two groups of models.
It has been established that a well-trained, Colonial pilot, even a nugget, can stand up to a Raider and win in most situations. The Raider's primary advantage seem to be in their massive numbers; while the Galactica carries around 40 Vipers, Cylon Basestars can support anywhere from 300 to 600 Raiders. The Raiders are also adept at maneuverability, once described by Kara Thrace as a "squirmy son of a bitch", and most pilots being unable to keep them in sight for more than a few seconds. The Raiders primary weapons are two kinetic energy guns mounted on the underside of their wings, close to the main body. They have also been seen to carry conventional missiles and tactical nuclear weapons. Raiders, by revealing their red "eye", can transmit deadly computer viruses or signals to enemy ships, which strike with brutal efficiency and have been seen to "shut down" Colonial vessels, turning off their power and making them useless and easy prey for the Raiders. If all else fails, Raiders will sometimes attempt suicide attacks against larger vessels, which have deadly consequences if allowed to hit, as seen when a single Raider spun out of control, hit and destroyed a sizeable civilian transport.
The original Cylon Raiders from the First Cylon War were larger spacecraft driven by Centurion pilots, and not alive themselves; these are used by the remaining First War Centurions guarding the Original Hybrid and the Cylon Colony, and are considered an obsolete design by current Cylons.
The modern Cylon Raiders are fighter craft and are not to be confused with Cylon Heavy Raiders. Like the raiders of the First Cylon War, the Heavy Raiders are transports and attack bombers, and are primarily piloted by Sixes and Eights, if not other models.
Humanoid Cylons 
Although they made only a single appearance in the original continuity (the episode "The Night the Cylons Landed" from Galactica 1980) humanoid Cylons play a major part in the reimagining. The term 'humanoid Cylon' is a description, rather than an official designation. These beings are usually just known as "the Cylons", or derogatorily as "skinjobs" or "toasters". These Cylons are indistinguishable from organic-humans due to their creation through synthetic-biology, meaning that they are made of real bones, flesh and blood rather than metal, but still possess a digital molecular-structure. In fact, some Cylons are initially programmed to believe that they are "organic" until revealed otherwise later in life. The Cylons have nonverbal ways of sharing information but do not have a hive mind, even among the identical duplicates, and are most often shown talking to one another. There are twelve distinct humanoid models in existence, which are divided into the "Final Five" that originated on Kobol, and "Significant Seven" (the latter term is only used by the Battlestar Galactica producers). The "Final Five" are unique, and are the last survivors of the thirteenth tribe. They developed the many copies of the "Significant Seven" in conjunction with the Centurions of the Twelve Colonies. Each copy shares basic traits with the rest of their model, but they can develop into distinct individuals.
Cylon society is made up of the seven surviving known, mass-produced humanoid models - Numbers One, Two, Three, Four, Five, Six, and Eight. The Number Seven model (the "Daniel" series) was destroyed by the Number One model (the "Brother John Cavil" series) decades prior to the destruction of the twelve colonies. The Final Five were killed, and temporarily boxed, by Number One, who then purged their memories and sent them to live among the humans. The remaining six models had no knowledge of the Final Five's identities, presumably blocked by Brother Cavil, though they were aware of the existence of five absent models not to be spoken of. When D'Anna (Three) attempts to learn their identities, her entire model's line is boxed — indefinitely deactivated with their memories permanently downloaded into cold storage — as punishment by Cavil (One). In the final episode of the third season, four of the final five are revealed to be "human" characters with long histories on the Galactica. Their purpose, and how and why they were hidden from the rest of their kind, is a major plot point of the fourth and final season. In the fourth season, Ellen Tigh is revealed to be another of the "Final Five".
The humanoid Cylons are responsible for command decisions. While the command structure has not been fully explored, some hints at organization have been revealed. At the end of the mini-series, a group of Cylons are debating what to do, and one speaks authoritatively, to which another responds, "by your command", a reference to the original series. Other forms of Cylon, such as the Centurions, the Raiders and the Hybrids, appear to have little or no policy-making role within their society to the point that the humanoid Cylons can freely impose blocks on their behavior and cognitive programming. Although the Cylons consisted originally of early-model Centurions fighting for freedom from slavery by humans, by the time of the series they are entirely subservient to their own humanoid creations. Later in the series, these restrictions are loosened within the "rebel" Cylon group; Centurions are occasionally depicted as resisting authority.
In the episode "Precipice", a Cylon council (made up of multiple copies of several models) appears to cast votes collectively by model, indicating that model plays an important role in the hierarchy of Cylon society and that they always make decisions in this fashion, as Cylons of the same model are implied to have higher or lower ranks than Cylons of other models at various times. It was also shown during the occupation of New Caprica, that a select group of humanoid Cylons, mostly ones who had been within the Colonies, such as Boomer and Caprica Six, seemed to have seniority within their own model. One of each model was seen deliberating and discussing their course of action, with each of the 'senior' copies representing the opinion of their entire model group. The Number Ones subvert consensus by undertaking many actions without the knowledge or consent of their siblings, such as turning against the Number Sevens and the Final Five, and then reprogramming their siblings to hide this.
Although little is known about Cylon psychology, it is clear that they share many of the same emotional vulnerabilities that humans possess. This is evidenced by Gina's catatonic state as a result of the severe trauma of her abuse at the hands of the Pegasus crew. This abuse was presented in the form of multiple sexual assaults, battery, starvation and outright torture. Number Six/Caprica Six also revealed that Cylons exist by 'projecting' an environment of their choice on the real/physical world.
Number One (John Cavil) 
The main antagonist of the series, John Cavil first appears on Galactica in the two-part episode "Lay Down Your Burdens", posing as a priest. His true identity is revealed when a second copy boards Galactica and reveals his Cylon nature. Cavil's role in society is one of contradictions and occasionally serves as a devil's advocate, pointing out the absurdity of his fellow Cylons and their religious zealotry. He was revealed to be the first model in the episode "Six of One".
Despite his talk of religion and his alter-ego as a priest, Cavil has a sadistic, cruel and Machiavellian streak in his personality which none of the other Cylon models share (going so far as to torture Saul Tigh by gouging out one of his eyes and showing it to him). He also took exquisite pleasure blackmailing Saul's wife (Ellen Tigh) into providing sexual favours in exchange for releasing her husband Saul from Cylon captivity on New Caprica. Cavil is also an atheist (the only one of the seven models who is one), and will often mockingly make quotation signs with his hands when saying the word "God". His opinions of humans are also driven by contradictions; despite being one of the most violently anti-human Cylon models, and even advocating a policy of culling humanity down to a "controllable number", Cavil claimed to have been against the destruction of the Twelve Colonies and advocates a unique Cylon Society, not one that emulates its creators. After finally arranging Colonel Tigh's release, Cavil manipulated the situation even further by again blackmailing Ellen Tigh to betray the human resistance on New Caprica and threatening to kill her husband if she did not comply.
Cavil is portrayed as being aloof compared to the other models, though it has been implied by Cylon Model 8 "Boomer" that Cavil has begun mentoring her with his philosophy regarding Cylons not emulating humanity. Cavil is aware of aspects of Cylon lore that the others models are not aware of; his knowledge of the "final five" led to him "boxing" Cylon Model Three D'Anna (as well as all other Number Threes) in order to ensure that whatever information about the Final Five she gained were "boxed" with her.
It is revealed in the fourth season that he and the other seven Cylon models were created by Ellen Tigh and the other four final five Cylons, and he was made in her father's image, as well as being given the name "John" by her. He hates this name and shows deep resentment towards Ellen at being 'limited' by having to live in a human-like body.
Cavil (John) was the first Humanoid Cylon created by the Final Five. Cavil with the help of the Final Five created the other six humanoid Cylons. Therefore Cavil knew about the Final Five all along. The Final Five showed the Centurions how to make Humanoid Cylons in attempt to give them human characteristics (love, mercy). The Final Five thought that these characteristics would prevent the same type of war that occurred on the thirteenth colony (the original Earth). For some reason, Cavil rejected the human trait of mercy and turned against the Final Five. Before the war on Caprica started, Cavil killed the Final Five by putting them in a compartment and then cutting off their oxygen. When the Final Five were resurrected and unboxed, John wiped their memories and implanted new memories for their life in the Twelve Colonies. He also altered the original programming of the seven other Humanoid Cylon models so that searching for, talking about, and even thinking about the Final Five became strictly forbidden.
Number Ones are played by Dean Stockwell.
Number Two (Leoben Conoy) 
Leoben first appears as a smuggler at the munitions depot at Ragnar Anchorage, where he was exposed as a Cylon in the mini-series. The Leoben model Cylons are known for their religious zealotry, which is intertwined with a pathological, and sometimes sexual, obsession with Starbuck. He was revealed to be the second model in the episode "Six of One".
Like his fellow Cylons, the Leoben models are skilled at deception and deceit. This was most notably seen when he manipulated Starbuck into thinking that a young girl he had kidnapped on New Caprica was her biological daughter. The Leoben models are known for their cunning minds and ability to find and exploit the weaknesses of others. As such, they are known to mix truth with their lies in order to better manipulate their victims. Unlike his fellows, he appears to have the ability of prescience and has on several occasions prophesied future events.
Number Twos are played by Callum Keith Rennie.
Number Three (D'Anna Biers) 
The Number Three model first appeared in the episode "Final Cut", as D'Anna Biers, a reporter for the Fleet News Service. President Roslin and Commander Adama grant Biers complete access to all areas of Galactica to investigate her suspicions of a military cover-up surrounding civilian deaths aboard the Gideon. Their belief is that Biers will discover that the military personnel have human faces and deal with the same pressures and fears as the rest of the fleet, and that the events on board the Gideon were just a tragic mistake. In truth, the Biers model used the documentary as a means to relay information regarding the Cylon Sharon being alive to her fellow Cylons back on Caprica. She was revealed to be the third model in the episode "Downloaded".
The Number Three Cylons are among the more aggressive Cylons of the seven models, as well as sharing a fate-based understanding toward the Cylon religion, believing that everything that happens is the will of God. Their religious devotion masks a deep questioning by Number Threes (in particular, the D'Anna Biers model) about why bad things are allowed to happen by God.
The Number Threes possess an "alpha-female" type aggressiveness, almost always forcing themselves upon other Cylons as the de facto leader in any situation that the Cylons engage in. They are often rivals of the Number One and Number Six models. The rivalry with the Sixes partly stems from when Caprica-Six beat one of the Number Threes to death to save Samuel Anders from being tortured and killed. D'Anna and Caprica-Six later reconcile and both of them are involved in a relationship with Gaius Baltar without any initial conflict. Baltar seduces D'Anna by exploring her crisis of faith, which leads to her secretly committing suicide (a major taboo in Cylon society) in order to go through the process of resurrection. She feels these near-death experiences will answer the burning questions regarding her faith, most notably the identity of the Final Five Cylons. This culminates in the episode "Rapture" in which D'Anna sees the faces of the Final Five (apologizing to one of them). Unfortunately, as she does so, the other Cylons voted to "box" not only D'Anna but also the entire Number Three line. Cavil, the Cylon who carried out the "boxing", revealed to D'Anna that she was being silenced because of what she saw regarding the Final Five and that her memories would be kept in "cold storage" as a result. D'Anna, but none of the other Threes, is unboxed in the fourth season episode "The Hub".
The Number Threes are also amongst the more anti-human Cylons, though for practical reasons: in "Exodus" Part II, D'Anna tells Baltar that she believes that humanity must die if only to prevent future generations of humans from seeking revenge against the Cylons for their acts of genocide and oppression against humanity. She is temporarily the leader of the "rebel" faction of Cylons which makes peace with the human fleet, but when the first Earth is found to be a devastated ruin, she decides to stay behind there and die rather than continuing to be part of the cycle of death, exodus, and rebirth.
Number Threes are played by Lucy Lawless.
Number Four (Simon O'Neill) 
Simon first appears in the episode "The Farm", posing as a human physician treating Starbuck for a gunshot wound in what was supposedly a resistance hospital on Caprica. In reality this was a Cylon "farm" set up to breed human-Cylon hybrids using captured humans, and he was also performing invasive tests on her reproductive organs. After Starbuck began to suspect Simon's true nature and killed him, she escaped from the facility and her fears were confirmed when a second copy of the model greeted her on her way out. He was revealed to be the 4th model in the episode "Six of One". Fours are consistently the Cylons' medical specialists.
Another Number four appeared in The Plan, posing as a married man in the Colonial Fleet. Cavil at one point asks Simon to leave his life behind and destroy the ship he lives on. He defies this order in order to protect his wife and her child by committing suicide and flying out of an air lock. He was not close enough to a Resurrection Ship and therefore died permanently.
Number Fours are played by Rick Worthy.
Number Five (Aaron Doral) 
In the miniseries, Doral appears as a public relations worker for the abortive Battlestar Galactica museum. In the episode "Litmus," another copy of Doral sneaks on board the Galactica and detonates an explosive. This event prompts the fleet-wide announcement that Cylons can have a human appearance. He was revealed to be the 5th model in the episode "Downloaded."
During the Occupation of New Caprica, the Fives seem to be one of the most anti-human and aggressive models. As a series, the Fives seem to specialize in public relations and control, using large scale events and media manipulation to their advantage.
Number Fives are played by Matthew Bennett.
Number Six (Caprica-Six / Shelly Godfrey / Gina Inviere / Natalie Faust / Lida / Sonja) 
The first model explicitly revealed to be a Cylon in the mini-series, the Sixes often use seduction to their advantage. Important copies include Shelly Godfrey, Gina Inviere, Head Six, Caprica Six, and Natalie.
One of the models, later known as Caprica Six, on her way to meet with Dr. Gaius Baltar, murdered an infant by breaking its neck. This could either be considered sociopathic, or a mercy killing due to the coming Cylon attack. She went on to save Baltar's life when his house was struck by a blast wave from the Cylon attack on Caprica.
Caprica Six has a love-hate relationship with Gaius Baltar, alternately defending him to other Cylon models or leaving him to suffer at their hands and progressing to reinitiating a sexual relationship with him.
Shelly Godfrey appeared in season 1's episode Six Degrees of Separation. She was a Number Six who was in Galactica after the Cylon attack. She accused Baltar of treason, by sabotaging human defenses, and therefore, being guilty of killing several millions of humans in that attack. She also appears in Battlestar Galactica: The Plan TV movie, which details a bit more her presence (and fate) aboard Galactica.
Another Number Six, Gina, acted as a contractor for the Battlestar Pegasus and was in a relationship with Admiral Cain. When Cain discovered that Gina was a Cylon agent, she ordered her crew to "push her programming" in an attempt to see if Gina was vulnerable to emotional trauma. Gina later escaped with Baltar's aid, assassinated Cain, and founded a resistance group in the fleet, preaching peace with the Cylons. While it seemed that Gina may have developed feelings for Baltar and was going to pursue a relationship with him, she detonated a nuclear warhead (provided by Baltar) which destroyed Cloud Nine, some other fleet ships, and generated an electromagnetic signature, the detection of which ultimately led the Cylon fleet to the new human colony on New Caprica.
A reincarnation of Baltar's Six (named Caprica Six by the others) committed the first incident of Cylon-on-Cylon violence in their history killing a Number Three with a rock in order to save the life of Samuel Anders, who himself was later discovered to be a Cylon.
With Caprica Six imprisoned on Galactica after helping Sharon (Athena) (Number Eight) escape from the Cylons with Hera, she offered to testify against Dr. Baltar. While in the brig, she has a relationship with Saul Tigh that results in the first Cylon-Cylon pregnancy.
It should also be noted that Caprica Six has a "Head Baltar" which only she sees similar to how Baltar has a "Head Six" that only he can see; Head Baltar serves as a sort of conscience for Caprica Six, but also an advisor in times of trouble or danger, much the same role that Head Six plays for Baltar. This Head Baltar has also appeared at least once to Baltar himself. Before the true nature of both Head Baltar and Head Six was revealed, there had been rampant speculation that Baltar was a Cylon. In the series finale, both Head Baltar and Head Six turned out to be divine beings (actually referred to as "Angels") manipulating both the Colonials and Cylons into fulfilling "God's plan."
Other important Sixes include Natalie, who originally led the rebel Cylon faction against Cavil's faction before being killed by Sharon Agathon in a misunderstanding, and Sonja, who was elected to represent the rebel Cylons in the Colonial fleet's Quorum of Ships' Captains.
Number Sixes are played by Tricia Helfer.
Number Seven (Daniel) 
Daniel was the seventh Cylon model created by the Final Five, as revealed in the episode "No Exit". Ellen referred to Daniel as an "artist, and so sensitive to the world". She was very close to Daniel, which enraged Cavil; he felt that Daniel was Ellen's favorite child and became jealous. Cavil poisoned the amniotic fluid being used to mature the Daniel copies and then corrupted Daniel's genetic code. This sabotage meant that no further Daniel copies could be created - an elimination more permanent than the later model-wide boxing of the Number Threes. The Sevens were not mentioned again during Battlestar Galactica's remaining episodes. Because of the destruction of this model line, there were twelve models active throughout the series rather than thirteen.
Because of the nature of the character(s), fans began to speculate that Kara Thrace was a version of the corrupted Seven line, or that her father was. Ronald D. Moore stated in the podcast for "Islanded in a Stream of Stars" that Daniel is merely a plot device to explain the missing number and to expand on Cavil's character (noting that Daniel is essentially the Abel to Cavil's Cain). In the podcast for "No Exit", Moore described the Sevens as a springboard for Caprica, the BSG prequel, where Daniel Graystone is the name of a main character played by Eric Stoltz; this Daniel is the creator of the Colonial Centurions.
Number Sevens are never seen in the series, and therefore not played by any actor.
Number Eight (Sharon "Boomer" Valerii / Sharon "Athena" Agathon) 
Sharon "Boomer" Valerii first appears as a Raptor pilot aboard the Galactica. Her true nature as a Cylon was only revealed at the end of the miniseries, and the series quickly establishes that Sharon acted as a sleeper agent, unaware of her true nature and programmed to carry out attacks on the fleet without her human side realizing what she was doing. She was revealed to be the 8th model in the episode "Downloaded".
Also interesting enough, at the end of the mini series, a number Six says "By your command" to an Eight. This phrase is usually spoken to the Imperious leader in the old series by Centurions. It seemed to give this particular Eight a leadership role.
The other significant copy of this model, Sharon "Athena" Agathon, married Karl "Helo" Agathon, rebelled against the Cylons and joined forces with the Colonials. Her child with Helo, a daughter named Hera, is the first Cylon/human hybrid to be born. Such a child is the subject of a Cylon prophecy and therefore very important as it was a 'child born of love'. Shortly after Hera's birth, Laura Roslin decides to mislead the Cylons into believing the child has died. Her plan involves lying to Athena and Helo, and giving the child to an adoptive mother, Maya. While aiding the Colonials in their plan to rescue the humans on New Caprica, Athena sneaks into a Cylon storage facility and steals launch codes for the civilian ships trapped on New Caprica by the Cylons. During this action, Athena is discovered by D'Anna Biers. D'Anna informs Athena that Hera is still alive, citing strange dreams and a prophecy by a human mystic as proof. Athena, believing this to be a ruse, kneecaps D'Anna. During the exodus from New Caprica, Maya is killed and the baby is found by D'Anna. Athena is later told, by Boomer, that Hera lives. Athena has Helo kill her, allowing her to download into a new body within the Cylon fleet. With the help of Caprica Six, she manages to rescue Hera and return to Galactica.
This model has been described as "weak" by Baltar's vision of Number Six, and Number Eights usually appear more compassionate and sympathetic than other Cylons. However, they fully supported the destruction of the Twelve Colonies; and the actions in particular of Boomer and an Eight who had a duplicitous affair with Felix Gaeta on New Caprica make it clear that Eights are capable of homicide and betrayal. Eights are also capable of intense loyalty and have the ability to break from Cylon traditions and laws to help human friends or family. They also voted to save humanity in the Cylon civil war started by Sharon (Boomer). She hesitated for a while when Cavil started to influence her, but in the end she chose to support the humans, even if it meant that she would have to give up her life. Sharon (Athena) became completely assimilated in human culture. Her child and husband became her focus in life. She seemed to be the only Cylon to accomplish a normal family existence. The model Eight's perceived fragility seems to camouflage great strength and direction. (In one episode, Sharon (Athena) was able to "hard" wire herself to the Galactica, hack into a Cylon fleet and shut them all down.) Eights seem to enjoy being with humans for the most part.
Number Eights are played by Grace Park.
The Final Five (Samuel Anders, Galen Tyrol, Tory Foster, Saul Tigh, Ellen Tigh) 
In the episode "Torn", Gaius Baltar questions Number Six as to why only seven humanoid models appeared on New Caprica and why he has seen only these same seven aboard the Basestar when she had told him previously that there were twelve models. Six replies that the Cylons do not talk about the other five models. Baltar has become worried that he may in fact be a Cylon himself and presses her on whether she would recognize one of the "Final Five", as he names them. Their conversation ends abruptly, leaving the truth of the other models unknown.
In the episode "Hero", Number Three has a dream immediately after she dies, where she sees five glowing figures. Later, in the episode "The Passage", she tries to hold on to the memory of their faces and draws pictures of them soon after downloading, but the memories fade and the drawings are too surrealistic to be of practical use. It is clear that she does not consciously know what the Final Five look like. In the episode "Rapture", D'Anna and Baltar reach the Eye of Jupiter and D'Anna receives a vision of the Final Five. She seems to recognize one of them, but the vision is cut short before the viewers see any detail of the figures. The shock kills her and upon awakening after downloading, she mentions her experience to Cavil. He confirms that the seven known Cylon models do not know who the Final Five are and that the pursuit of that information is strictly forbidden by their programming. As punishment for this and for other acts, Cavil then terminates her and her entire model is "boxed", taking the secret of the Final Five with her until she is unboxed.
In "Crossroads", four of the final five Cylons are revealed to themselves, each other, and the audience, though not to the human characters. Samuel T. Anders (Michael Trucco), Galen Tyrol (Aaron Douglas), Tory Foster (Rekha Sharma), and Saul Tigh (Michael Hogan) begin hearing the same hallucinatory music that no one else can perceive (a version of "All Along the Watchtower"). When the music draws them towards each other, a "switch goes off" in their minds and they realize that they are all Cylons. They resolve, nevertheless, to continue doing their duty as part of the fleet. The identity of the fifth and final Cylon remains unknown even to them. Their "awakening" seems to affect other Cylons as well, as in the episode "He That Believeth In Me", a Cylon Raider scans Anders then disengages the attack; in the same episode, aboard Galactica, Caprica Six tells Roslin that she can feel the Final Five and that they are near. It is later revealed in "Six of One" that the Twos, Sixes and Eights believe that the Raiders called off the attack because they sensed the Final Five, something the Ones, Fours, and Fives disagree with. Cavil further claims that their original programmers programmed the seven Cylon models not to seek that information out. This disagreement leads directly to the Cylon Civil War, in which the Twos, Sixes, and Eights become known as the rebel faction. In "Revelations", an unboxed D'Anna reveals that only four of the Final Five are within the Colonial Fleet, and confirms that Tigh, Tyrol, Anders, and Foster are those four Cylons. A standoff between Galactica and the rebel Baseship results in the four being exposed as Cylons to the rest of the human Fleet, but Lee Adama, in his capacity as acting President, grants them amnesty as part of an alliance between the Fleet and the rebel Cylons.
Ronald D. Moore confirmed in an interview that the four are indeed fully Cylon — although "fundamentally different" from the others. Moore has also stated that unlike the other Humanoid Cylon models, the Final Five do not have model numbers. This is because in their original lives they were born to Cylon parents through sexual reproduction, rather than being built, as stated in "No Exit".
In "Sometimes a Great Notion", it is revealed that all of the Final Five had previous lives on Earth, 2000 years in the past, as part of the Thirteenth Tribe. Cylon testing procedures used on the tribe's remains reveal that they were all humanoid Cylons. As each of the Final Four explores the ruins, each begins to regain small memory fragments of their past life. It is when Saul Tigh remembers a snippet of his previous life that he discovers that his late wife, Ellen Tigh (Kate Vernon), must be the fifth and final Cylon, because she was present on Earth 2000 years ago as well. During Saul's flashback, his wife insinuates that she had foreknowledge of the destruction of Earth when she states that plans have been made for her and Saul to be reborn.
In "No Exit" Ellen Tigh is revealed to have resurrected onboard one of the Resurrection Ships in the Cylon fleet after her poisoning, and to have subsequently been held prisoner by Cavil on a Basestar for 18 months. The past of the Final Five is also revealed: they lived on Earth 2000 years ago and were researchers in rebuilding Cylon resurrection technology, which had been abandoned when the Thirteenth Tribe gained the ability to procreate. Saul and Ellen were married even back then, while Tyrol and Foster were in love and had plans to get married. The five learned of the upcoming holocaust from beings only they could see and worked to rebuild Resurrection. They succeeded and placed it on a ship, which they left in orbit of Earth. When the nuclear attack happened and they were killed (according to the series' writers, the cataclysm was an uprising of Earth's own Centurions that apparently destroyed both sides), they were reborn in new bodies on that ship in orbit. The Five then headed for the Colonies to warn them about making artificial life, but the trip took thousands of years due to there being no FTL drive on their ship. Due to traveling at near light speed, time dilation made it seem like less than that to them. They arrived during the first war, unbeknownst to the humans, and made a deal with the Centurions: stop the war and they would help them build human bodies. Thus the Final Five ended the First Cylon War. They built Number One, Cavil, and he helped them build seven other models, but after Ellen began to favour Number Seven, Cavil permanently destroyed the Number Seven line by contaminating the production. Ultimately Cavil locked the Final Five in a compartment and evacuated the oxygen, killing them. He then boxed them and apparently removed the memory of their identities from the other Cylons. He later unboxed and resurrected them, but first blocked their true memories and implanted false ones. Cavil periodically seeded them among the human populations starting with Saul, and then Ellen, to show them how bad humanity supposedly was. This shows that Cavil's claim that not seeking out the Final Five was a directive from the Cylons' original programmers was a lie, and that he was only pretending not to be aware of their identities himself. Ironically, the "Final Five" are in fact the first five humanoid Cylons to encounter the Colonials and the new Cylon Centurions after the Thirteenth Tribe's diaspora. Of the Five, only Anders and Ellen regain their true memories: when Anders gets shot in the head, it seems to break Cavil's block on his memory and Ellen's resurrection in a new body restores all of her memories. It is also revealed in The Plan that the Cavils planned for the Five to die in the destruction of the Colonies, download, regain their true memories and apologize for their faith in humanity. Despite the Cavils' hopes, the Final Five survived the destruction of the Colonies without resurrecting (which the Cavils hadn't believed possible) and Cavil even keeps Ellen alive so she can suffer more and learn her "lesson". The Cavils' hopes that the Five learn a "lesson" is shown not to have worked, as all of the Five (except maybe Tory Foster) maintain their loyalty to humanity even after the truth comes out.
Similar to their role in ending the First Cylon War, the Final Five have a major role in ending the second war. During the Battle of The Colony, the Five take a prominent role in the battle, especially Anders who, acting as Galactica's Hybrid, shuts down the Colony's weapons and Hybrids. The Five also nearly bring a peace between human and Cylon by exchanging Resurrection technology (which can only be rebuilt by the Five combining their knowledge together) for peace. However, a side-effect of the connection they make is they see each other's memories, and Tyrol learns that Foster murdered his wife. In response, he strangles her, and the temporary peace is shattered. Later, Anders flies the fleet into Earth's Sun, destroying the fleet and himself, leaving only three of the Final Five alive. As the Resurrection Hub had been destroyed, their deaths are permanent.
The Hybrids resemble human beings inside an immersion tank similar to a Cylon rebirthing tank. The Hybrids do not have a completely human body, but rather appear to be more like cyborgs, consisting of conduits and other connectors mated to, or in place of elements of their bodies. The Hybrid is not one of the "twelve models" of humanoid Cylon, but is a separate model that effectively further bridges the gap from primarily mechanical Centurion, to partially bio-mechanical Raider, to Hybrid, to humanoid Cylon. They are similar to the autonomous bio-mechanical pilots within Raiders, specially constructed as living computers that manage the autonomic functions of the basestar, including navigation and FTL jumps and climate control. The Hybrids are so integrated into the basestar's functionality that they are, for all practical purposes, the basestar itself.
In addition, the Hybrids continually speak what most of the humanoid Cylons consider to be gibberish, although there is some difference of opinion on this point. Many Cylons believe a hybrid's conscious mind is completely mad and the functions it performs are part of a deeper state of mind in connection with the ship. Caprica Six states that the Leoben Conoy models believe that every word a hybrid says is channeled from the Cylon god. A Hybrid is not allowed a vote in the Cylon democratic process by the humanoids, though it sometimes objects to the course of action they take, for example, leaving another basestar full of disease-infected Cylons to their fates.
In Battlestar Galactica: Razor another Hybrid is seen. This Hybrid, considered the First Hybrid in Cylon lore, was the result of experiments on humans during the first Cylon war and appears to be more coherent and prophetic than the other Hybrids. It went rogue as early as the end of the First War, and is protected by model 0005 Cylons called Guardians, who consider it their god. According to the humanoid Cylons, the very existence the First Hybrid and its Guardians was considered more of a legend. The Colonial Fleet accidentally clashes with the Guardians and manages to destroy them and First Hybrid along with its basestar. The First Hybrid has the appearance of an old man, whereas the standard Hybrids look like young women and are identical.
After being shot in the head and entering into a vegetative state, Samuel Anders is hooked up to a datastream and as a result develops Hybrid-like abilities, acting as the Hybrid for Galactica. When hooked up, he speaks and acts like a Hybrid and at one point is referred to as Galactica's Hybrid. This shows that apparently under special circumstances, normal Cylons, or at least Final Five Cylons, can become Hybrid-like beings.
In his Battlestar Galactica Podcast, Ronald Moore explained that the Hybrids should be considered an intermediate step between humanoid and mechanical model Cylons. They are not to be confused with the hybrid human/Cylon child Hera Agathon.
Humanoid Cylons, except for the Cavil models, follow a monotheistic religion. Religious fanaticism partially motivates their genocide of humanity, and despite their origins, the Cylons believe themselves to be spiritual beings. This monotheism seems to share some of the characteristics as the Abrahamic religions: belief that God is omniscient, omnipotent, omnibenevolent, that he will one day deliver divine retribution, and that he intervenes in the mundane world.
The different models of Cylon have slightly different ways of talking about and dealing with their god, reflecting the different aspects of humanity that each Cylon model reflects. As shown in at least one case, the Number Ones in season four, the Cylons do not all believe in god and can be agnostic or atheist. In contrast, Leoben Conoy (model Number 2) is fanatically religious, even compared to the other Cylon models.
Cylons seem to be physically stronger than humans. While this is obvious with respect to Centurions, the extent to which this is also true of humanoid Cylons is unclear. In the miniseries, William Adama fought in hand-to-hand with a number two who, despite suffering from the effects of radiation, proved to be physically stronger than Adama. The number two managed to break off a metal pipe to use as a club and lift Adama off the floor with one arm. In the episode "Flesh and Bone", another number two was able to break apart a pair of metal handcuffs while under interrogation. In the first season finale, "Kobol's Last Gleaming II", a Number Six engaged Kara Thrace hand-to-hand and proved to be exceptionally fast, agile and strong. Despite these demonstrations of physical strength and dexterity, humanoid Cylons are vulnerable to most of the same things as humans. The number two who fought Adama was beaten to death with a flashlight while the number six who fought Thrace was impaled by a piece of rebar. While humanoid Cylons may be at the peak of human physical strength even perhaps exceeding it, they do not appear to be superhuman and trauma which would cause severe injury or death in a human can be expected to do the same to a Cylon. Cylon skin appears just as vulnerable to breaking as human skin, with the resulting injury bleeding just as a comparable wound would in a human.
A Cylon's psychology is sufficiently similar to that of a regular human to allow for manipulation. Admiral Cain and Kara Thrace exploited this fact whilst 'interrogating' Cylons. The experience of being killed is traumatic and can leave deep emotional damage in a Humanoid Cylon.
Cylons are highly susceptible to an ancient virus which can be transmitted by rodents but which humans have developed an immunity to, lymphocytic encephalitis. This virus was carried on a beacon left by the Thirteenth Tribe at the Lion's Head Nebula millennia ago and disrupts all organic Cylon technology including Raiders, Hybrids (which in turn disrupts Centurions) and humanoid Cylons. The humans speculate that the beacon was accidentally contaminated when someone sneezed. The Cylons believe that a critical symptom of this virus, a harmful bioelectric feedback, can be transmitted during a download and have so far prevented any Cylons infected from being downloaded into a resurrection ship. The only Cylon found to be immune is a Number Eight copy, Sharon "Athena" Agathon who had given birth to a half-human child and thus 'inherited' human antibodies from her offspring (Although it is unclear if she retained this ability after she downloaded into a new body that had not given birth).
Dr. Cottle developed a vaccine to the virus which had infected a number of humanoid Cylons on a basestar near the Lion's Head Nebula. The RNA of the vaccine broke down in the blood stream of a Cylon humanoid model by their own immune response, forcing regular injections to keep an infected Cylon healthy. The Cylons themselves have not managed to develop an antidote or vaccine to the virus.
The silica pathways of humanoid Cylons are affected by certain forms of radiation, such as that surrounding Ragnar Anchorage. It is assumed but not stated that this radiation affects all types of Cylon as the station was chosen as a refuge by Commander Adama before he learned of the existence of biomechanical models and the radiation had deleterious effects on the Number Two model they found at Ragnar Anchorage (Although he was still strong enough to engage Adama in a fight and break a metal pipe before he was killed). This also suggests that humans are not vulnerable to the effects of this radiation. In addition, plutonium is used for Baltar's Cylon Detector because its radiation affects humans and Cylons differently. The detector was dropped as a plot device early in Season 2 as the revelation of Boomer (who had been a beta test subject) as a Cylon convinced the command staff that the detector did not work (Dr. Baltar lied about Boomer's test results because he feared the consequences if she learned of her identity while alone with him).
See also 
- Cylon vessels
- Basestar — controlled by Hybrids
- Raider — individuals in their own right
- Heavy Raider
- Resurrection ship
- Caprica pilot
- Caprica episode "Know Thy Enemy"
- Season three
- Season four
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- [DVD commentary with Kevin Murphy, Caprica Executive Producer ("Apotheosis")]
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- "BATTLESTAR GALACTICA - Season 4 Mid-Season Finale "Revelations" Screening". Daemon's TV. 2008-06-11. Retrieved 2010-01-24. "MOORE: The final 5 don't have numbers and the number 12 is repeated but there is no direct correlation."
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