Chaos Space Marines
In the table-top wargame Warhammer 40,000, the Chaos Space Marines or Chaos Marines, are Space Marines who serve the Chaos Gods. They are also referred to as the Traitor Legions, primarily in background material written from the perspective of the Imperium.
The background shown in both Codex: Space Marines (Haines and McNeill, 2004) and Codex: Chaos Space Marines (Chambers et al., 2002) states that the Chaos Marine Legions were nine of the twenty Legions of Space Marines who fought in the Great Crusade for the Imperium of Man. At this time the Warmaster Horus, first among the Primarchs, and the Luna Wolves Legion (later the "Sons of Horus") were corrupted by Chaos and instigated the galaxy-wide civil war known as the Horus Heresy.
Further background to the Chaos Space Marines is explored in detail in the 'Horus Heresy' series of novels. After the death of Horus and the end of the Heresy, the remnants of the nine Legions along with the other Imperial forces that had joined Horus escaped to a warp-infested area of the galaxy connected directly to the Immaterium that is known as the Eye of Terror. Due to the nature of Chaos, and the temporal instability of the Warp, the very same Chaos Marines who revolted against the Emperor continue to fight against the Imperium.
The Legions have kept their old names, with the exception of the Sons of Horus who were renamed the Black Legion by their new leader, Abaddon the Despoiler. Besides Horus, two other Chaos Primarchs were believed to have been killed during or shortly after the Heresy (Konrad Curze of the Night Lords and Alpharius of the Alpha Legion.) The seven surviving Primarchs have since become Daemon Princes. These daemonic Primarchs rarely take part in the affairs of their Legions or any part of the Warhammer 40,000 universe. For example, Magnus the Red, Primarch of the Thousand Sons is the most powerful of all the Daemon Prince sorcerers. Yet he rarely enters the battlefield, even though prior to the Horus Heresy he always took part in his Legion's battles and was a determined warrior. Angron however, Primarch of the World Eaters, led an invasion force in what was to become the First War of Armageddon. Some of the Legions have pledged a particular loyalty to one of the four Great Chaos powers but the eight Blood Lords are loyal to Angron alone. The same is the case with the Death Guard, where the Primarch Mortarion's war council is known as the Lords of Decay. Abaddon the Despoiler has taken charge of the Sons of Horus, now known as the Black Legion. Abaddon is the only Chaos Marine since Horus to be able to command the loyalty of all nine Traitor Legions (albeit, temporarily after intense bargaining), and has led thirteen Black Crusades against the Imperium of Man.
A Black Crusade is composed of all the mustered forces of Chaos, from traitor space marine legions to heretical imperium citizens. It is believed to be the one true path to gain the favor of the Chaos Gods. A Black Crusade can be dedicated to a particular Chaos God in order to invoke their blessing and appease the Warmaster's or the heretics' patron. However, one should be careful in dedicating a Black Crusade to a particular Chaos God or multiple Chaos Gods as the Gods are protective of their champions' achievements and jealous of each other. Since M32 (the 32nd Millennium), there have been a total of 13 Black Crusades.
- 13th Black Crusade: Arguably, the thirteenth Black Crusade is the most, if not only totally successful Black Crusade yet, with others believing that it signals the end times for the Warhammer universe. It began during the year 999 of M41, when multiple sightings of space hulks were reported. Abaddon the Despoiler raised the greatest Chaos Army since the Horus Heresy and initiated the largest clash between Imperial and Chaos forces since the Horus Heresy.In the end, it resulted in massive casualties on both sides, with the forces of Chaos prying the powerful fortress world of Cadia out of the hands of the Imperium, a feat that had never succeeded before. Cadia is known as having the only known stable warp-route out of the eye of terror, and in addition to its substantial imperial military presence also contains the Cadian pylons- massive structures that are responsible (unbeknownst to the Imperium until the 13th black crusade) for restricting the eye of terror's growth, and was revealed to have been built by the Necrons, and thus was strategically important to attack for Abaddon if the crusade was to make any meaningful headway. During the final battle on Cadia Abaddon ordered a blackstone fortress (an ancient Xenos space station that predates the Imperium, possibly a creation of the Old Ones) flung to the surface of the world, destroying Cadia and creating the Great Rift, known as the Cicatrix Maledictum by the Imperium, a massive galactic-scale dimensional tear in reality to the warp-which destroyed countless inhabited star systems. The Great Rift also means that virtually every world of the Imperium, even Terra, is engulfed by conflict. 
Gods of Chaos
- Khorne: Khorne is the Chaos God of war, blood, and violence, and personifies the emotions of hatred and blinding rage. He acts outwardly by seeking the deaths of others, preferring close combat over ranged weaponry, and the only things he respects are strength and martial prowess. Khorne's followers are always ferocious warriors. Men turn to Khorne for martial power and the strength to conquer but he doesn't care for his followers or from where the blood flows, only that it does as he sits upon a throne crafted from the multitudes of skulls from enemies and allies alike. He openly despises magic in all its forms, believing it to be effeminate, weak, and the craft of cowards.
- Nurgle: Nurgle is the Chaos God of death and mortality, embodying disease and rot, and personifies the emotion of despair. His power comes from the inevitability of death and decay, and Nurgle is often referred to as 'Grandfather Nurgle', as entropy is the most ancient of forces, and he is the only one who outwardly shows care for his followers. Nurgle's followers are granted power by their acceptance of this reality. Nurgle prides himself on the achievements of his followers, gifting them with hideous diseases while sheltering them from pain, and his followers rejoice in their blessings, shrugging off lethality and disfigurement in a state of rapturous undeath. Tzeentch is his equal and opposite, and the two will frequently battle each other.
- Tzeentch: Tzeentch is the Chaos God of change, revolution, knowledge, vigour, and sorcery, and is the personification of hope or ambition. His titles include the Changer of Ways, the Architect of Fate and the Great Sorcerer. Tzeentch excels in subtle machinations and is patron to schemers and conspirators of all sorts, favouring the cunning and the wise over the strong. He is also among the most progressive and enlightened of the Chaos Gods, seeking betterment and refinement, though he ultimately manipulates his followers and betrays those who become useless to him.
- Slaanesh: Slaanesh is the Chaos God of lust, pleasure, and satisfaction, and personifies desire. A sensuous, androgynous deity that is simultaneously referred to as male and female, Slaanesh is associated with hedonism and decadence. It is known by many colourful names such as The Prince of Pleasure, She Who Thirsts, and the Lord of Excess. Slaanesh is said to be both the youngest and weakest of the four Chaos gods, though early in its existence it was far stronger, and murdered and consumed nearly the entire pantheon of Eldar gods. Slaanesh's creation was due to the sum of the Eldar's own excesses over millennia, due to their uniquely powerful psychic presence in the Warp, excesses described as equal parts hedonism and painful delight. This event led directly to the near-extinction of the Eldar, and the creation of the Eye of Terror. Mortals who seek charisma and fellowship follow Slaanesh, for its mark makes one popular and inspiring, though its followers are just as likely to be terrifying orgiastic maniacs. For this reason, the followers of Slaanesh are known to be particularly dangerous, as they seek pleasure with hopeless abandon in all martial actions, even those actions considered suicidal by any sane commander.
Although those are the main Gods of Chaos, there are others such as Malice, God of Anarchy and Self-Destructive Forces. Some haven't even been referred to. These are just the four Ruinous Powers. Also, these gods have their equal and opposite, and frequently battle each other. Nurgle and Tzeentch oppose each other, as Nurgle embodies the static and inevitability of death while Tzeentch is the personification of change and hope. Devotees of Slaanesh and Khorne frequently battle each other, since Khorne exists solely for the glory of combat – followers of Khorne favour might and brute strength over all, while Slaanesh exists solely for pleasure - The followers of Slaanesh embody excess in every way.
Forces of the Chaos Space Marines
Each of the Chaos Space Marine Legions specializes in a different type of warfare; each of the major Chaos Gods have a legion dedicated to them. The rules for the Chaos Space Marines are currently in their 6th edition, one of the few codices that have not been updated towards 7th edition (though both the Black Legion supplements and the Crimson Slaughter supplements have been updated).
The Chaos Space Marine Traitor Legions are as follows:
- Emperor's Children, once the III Legion of the twenty original Space Marine legions. Their primarch, Fulgrim, was dedicated towards the pursuit of perfection and was said to have given a speech so eloquent that his legion was given the honor of bearing the Emperor's Aquila as their symbol. During one of the Emperor's Children's missions against a xenos race called the Laer, Fulgrim was possessed by a daemon trapped within his sword. He later freed himself and joined Horus as leader of one of the original traitor legions. Driven by hubris and pride, the Emperor's Children later became devotees of the Chaos God Slaanesh, making extensive use of Noise Marines, armed with exotic Sonic Weaponry.
- Iron Warriors, once the IV Legion of the twenty original Space Marine legions. Their primarch, Perturabo, grew increasingly jealous of his brother primarchs, particular Rogal Dorn, primarch of the Imperial Fists. Specialists of siege warfare, they often came into conflict with the Imperial Fists, who also specialized in siege warfare. After a series of unrecognized, grueling attrition battles in which the Iron Warriors became more and more disillusioned, they turned to chaos and willingly joined Horus against their brother marines. After a series of civil wars, they have split apart into numerous warbands, with Perturabo himself achieving daemonhood and retiring to Medrengard, his personal planet filled with large metal fortresses belching smoke and fire. They possess a large number of daemon engines and Obliterators, hulking monstrosities of flesh and metal who can create any weapon they desire from their bodies.
- Night Lords, once the VIII Legion of the twenty original Space Marine legions. Their primarch, Konrad Curze (more commonly known as Night Haunter), grew up in the dark world of Nostramo, and took power of the planet's populace by executing and flaying all the criminals that stood in his way. The Night Lords became the most terrifying of the Space Marine legions; whole rebellious worlds surrendered at the knowledge of their arrival. Their primarch was also cursed with multiple visions, including one foreshadowing his own death, thus leading him further into insanity. After discovering that his homeworld had returned to anarchy after his campaign of terror to pacify them along with the fact that the Nostroman psychopaths who replaced the legion's losses were polluting the Night Lords, he ordered the destruction of his homeworld before fleeing to join Horus. After the Horus Heresy, he allowed himself to be killed by an Imperial assassin, wanting to prove that even the Emperor was willing to resort to such dishonorable actions. Unknown to the rest of his legion, Curze secretly despised his own legion, as they were made up of murderers and killers. The Night Lords currently are a united group of marines specializing in terror attacks, and so possess a large number of Raptors, chaotic versions of jet pack equipped assault marines.
- World Eaters, once the XII Legion of the twenty original Space Marine legions. Their primarch, Angron, grew up in the gladiator pits of Nuceria, and plotted a mass rebellion against the planet's rulers. The Emperor rescued him at the last moment, however, leading to his army's destruction and a deep rooted resentment of the Emperor for denying him an honorable battle alongside his gladiator brethren. Refusing to accept his legion, he killed the first seven captains before the eighth, Kharn, managed to earn his respect. Christened the World Eaters, Angron's legion was known for their relentless savagery in battle. Having been under Imperial pressure and already bloodthirsty thanks to the mental implants known as the Butcher's Nails, they willingly joined Horus and partook in his rebellion against the emperor. The legion's unity was shattered by their Champion Kharn attacked his comrades in a rage for accepting a ceasefire with another Chaos Legion during a civil war, leading to infighting that caused them to split into smaller warbands. Angron later achieved daemonhood, and currently resides in the Warp. The World Eaters now are devoted to the Chaos God Khorne, boasting more Khornate Bezerkers then any other legion.
- Death Guard, once the XIV Legion of the twenty original Space Marine legions. Their primarch, Mortarion, was raised by a warlord on a planet filled with noxious fumes, before rebelling against his adoptive father and finding solace with the enslaved populace of the planet. Having been saved by the Emperor from the warlord and denying him his chance to kill him, Mortarion gained a legion who specialized in biological warfare. Having been disillusioned by the Emperor's goals and believing him nothing more than a drunken tyrant, he was brought into Horus's rebellion and joined Horus as one of the four original legions who betrayed the Emperor. Known for their incredible fortitude, the Death Guard fought across the most noxious and hazardous war zones unscathed. Having been tricked by Typhus, the First Captain, into the Warp and besieged by plagues from all sides, Mortarion swore devotion to the Chaos God Nurgle and the Death Guard became fully swollen with disease and death. Having achieved daemonhood later on in history, Mortarion retreated to the Plague Planet which he now spends his time creating new plagues for his master. The Death Guard is composed largely of Plague Marines, specialists in biological warfare and disease.
- Thousand Sons, once the XV Legion of the twenty original Space Marine legions. Their primarch, Magnus the Red, was distrusted by all the other Space Marine legions, in particular the Space Wolves, because of their frequent use of magic and the powers of the Warp. Upon learning of Horus' corruption, Magnus sought to warn the Emperor with forbidden warp powers; only to unknowingly breach the Emperor's secret Webway portal Project. To make things worse, the Emperor refused to believe Horus turned traitor and sent the Space Wolves to apprehend the Thousand Sons for trial. Unfortunately, the Space Wolves were tricked by Horus into purging the Thousand Sons on their homeworld of Prospero. With his cities burning and his soldiers being slaughtered, Magnus had no choice but to swear fealty to the Chaos God Tzeentch, escaping into the Warp. Because of their frequent use of the Warp's magical energies, the Thousand Sons were cursed with frequent mutations, thus they historically numbered usually no more than a thousand Space Marines before Magnus' arrival. After a period of stability due to Magnus' use of warp powers, the mutations returned tenfold after turning to Chaos. In order to stop these mutations, their chief librarian Azhek Ahriman secretly cast a powerful spell which stopped the mutations while enhancing the powers of all psychic marines. However, the spell inadvertently turned the non-psychic marines into dust and bound their souls inside their Power Armors; reducing them to semi-distant automatons known as Rubric Marines. Of all Chaos Space Marine legions the Thousand Sons possesses by far the most Chaos Sorcerers.
- Black Legion, once the XVI Legion of the twenty original Space Marine legions. Formerly the Luna Wolves, their primarch, Horus Lupercal, was the first primarch discovered by the Emperor and was raised alongside his birth father, becoming the Emperor's most trusted primarch. After all the other primarchs were discovered, Horus was named the Warmaster and was granted command of all the Space Marine legions. He renamed his own legion the Sons of Horus, but a twinge of doubt existed in him as the Emperor kept secrets from Horus regarding the reason why the Emperor left the Great Crusade. After an accident which resulted in the Word Bearers manipulating Horus to fall under Chaos's sway, Horus openly declared a rebellion against the Emperor, instigating the Horus Heresy. After a series of attacks, most notably the purging of loyalists from the traitor legions on Isstvaan III and the decimation of the loyalist legions on Isstvaan V, Horus finally faced off against his father on the Emperor's warship, and was killed by the Emperor. In shame, the Sons of Horus painted their armor Black, renamed themselves the Black Legion, and fled back into the warp. Now Ezekyle Abaddon, the First Captain of the Sons of Horus, has sought to reunite all the forces of chaos under him in a bid to destroy the Imperium, christening himself the Despoiler. He has launched thirteen Black Crusades against the Imperium, the most recent being the setting of the current 40K universe. The Black Legion is also the largest and most infamous of the Chaos warbands, and quite possibly the most powerful.
- Word Bearers, once the XVII Legion of the twenty original Space Marine legions. Their primarch, Lorgar Aurelian, venerated the Emperor as a god, but was censured and made example of because the Emperor rejected religious superstition through the "Imperial Truth". Having grown disillusioned, Lorgar ventured into the Warp to seek new gods to believe in, discovering new masters in the Chaos Gods-who claimed they were vital to humanity's survival, and became the first legion to fall to Chaos. They orchestrated Horus's corruption and the entire Horus Heresy. Lorgar himself later achieved daemonhood, and the Word Bearers fractured after the end of the Heresy. Currently they make extensive use of daemons and possessed Space Marines, and also have a lot of Dark Apostles, priests who guide the members of the Word Bearers further in to the veneration of the Chaos Gods.
- Alpha Legion, once the XX Legion of the twenty original Space Marine legions. The last primarch to be discovered, Alpharius had a secret unknown to everyone: he actually had a twin named Omegon. The Alpha Legion was primarily used for secret missions, as they were known for their use of deception and subterfuge. It is said that after being revealed the future by an alien race, Alpharius joined Horus in his betrayal of the Emperor as a secret bid to finally eradicate Chaos from the universe. After the Heresy one of the two primarchs was said to have been killed by Guilliman, the primarch of the Ultramarines, while another may have been secretly killed by Rogal Dorn on Pluto. However, knowing the Alpha Legion's frequent lies and dissent, no one knows if one of them really survived or whether both survived. The Legion frequently uses Chaos Cultists for infiltration and sabotage, spreading throughout the universe in a web of lies and deceit.
Alongside the Traitor Legions, there have been many Space Marine Successor Chapters who have also fallen under the sway of Chaos. Some of the most notable ones are as follows:
- Red Corsairs, once the Astral Claws, their chapter master Lufgt Huron, powerhungry and seeking to create a legion sized force of Astartes, led several other chapters in a rebellion against the Imperial after the Heresy into what would later been known as the infamous Badab War. After being injured and nearly killed, Huron fled to the Warp alongside his chapter and were rechristened the Red Corsairs, with their leader becoming Huron Blackheart, the Tyrant of Badab. The Red Corsairs have amassed a massive pirate fleet, becoming a force to be reckoned with, rivaling that of the ancient traitor legions.
- Crimson Slaughter, once the Crimson Sabres, their chapter master Sevastus Kranon led their chapter on a crusade in the Warp, severing all connections with other Space Marine chapters though remaining loyal to the Imperium. After a massacre on Umidia however, the chapter was cursed by the Chaos God Khorne and forced to suffer painful hallucinations of all the people they killed. Driven mad by these unending visions, the Crimson Sabres found a moment of peace in their minds when conducting genocides. Forsaking the Imperium and renaming themselves the Crimson Slaughter, this warband is featured in Warhammer 40,000's starter set, Dark Vengeance, led by the Chaos Lord Kranon the Relentless.
- The Forsaken. In an event that will be known as the Abyssal Crusade, thirty Space Marine chapters were sent into the Warp on a mission under the influence of an Imperial Saint named Basillius (later revealed to be a Chaos worshiper and executed), and only one managed to return loyally the Imperium. The rest of these chapters became Chaos warbands or were completely killed. Some notable warbands are the Death Shadows, the Iconoclasts, and the Vectors of Pox.
The legions are often featured in short stories and novels published by Games Workshop's publishing arm, The Black Library.
Since the Horus Heresy, many Space Marine Chapters have been corrupted in one way or another by Chaos. No specific rules exist for renegade chapters, allowing players to adapt other rules to represent their forces. According to the records of the Ordo Malleus (the Inquisition branch body responsible for protecting the Imperium from Chaos and daemons), approximately 50 chapters have turned renegade after the Horus Heresy; however, the accuracy of this number is doubtful. Examples of given Space Marine chapters include the Sons of Malice, the Damned Company of Lord Caustos, the Violators, the Steel Cobras, the Thunder Barons, the Sons of Vengeance, the Silver Guards, etc. Beside those chapters the forces of chaos are also strengthened by individual corrupted companies or detachments from loyalalist Space Marine chapters; forming smaller warbands or joining other renegade chapters.
Differences between Chaos Space Marines and Space Marines
The Chaos Space Marines have the same origins as the Space Marines. Due to their allegiance to Chaos, Chaos Marines can be mutated or willingly possessed (except for the Thousand Sons Rubric Marines), thus making themselves into monsters, faster or otherwise superior to the Space Marines and other inhabitants of the Warhammer 40k universe. Chaos Marines have extended lifespans due to the time-warping effects of the Eye of Terror, and the fact that space marines as a whole are unable to die of old age, and their millennia of experience gives them levels of mastery with more advanced skills and tactics that Loyalist Space Marines do not have. However, they are inhibited by their own anarchic nature, limited numbers, and constant infighting. If they were to organize and form an army equivalent to the tactical army of the Imperium, they would be a greater threat than they are now. Abaddon of the Black Legion seeks to unite all of the Chaos forces and lead them to a last Black Crusade against the Imperium.
However, due to the hostility of chaos space marines toward each other,other legions and warbands, it took Abaddon 13 Black Crusades to finally cause significant damage towards the Imperium by launching a full-scale attack and occupation of Cadia.
Chaos Marines are equipped with the power armour and weapons they had when they initially betrayed the Imperium, which are broadly the same as those used by Space Marines (although some differences now exist). The current setting of the Warhammer 40,000 game is about 10,000 years after the Horus Heresy, and, while the Imperium has made some technological advancements, Chaos Marines have far more limited access to the handful of new inventions that have appeared on the galactic scene. For example, Iron Warriors are known for capturing and using Imperial tanks. This is not a strong differentiating factor though, as the Imperium merely replicates or rediscovers technology designed during the "Golden Age of Technology" (also known as the "Dark Age of Technology") and has very little understanding of it; thus there have been very few developments during the last 10,000 years.
- The death metal band Debauchery released several tracks/albums with references to the World Eaters. Most notable is the track "KILL MAIM BURN!".
- The British death metal band Bolt Thrower released a song titled "World Eater" on their album Realm of Chaos. The entire album is, in fact, themed around the Warhammer 40,000 concept of Chaos, as evidenced by the Games Workshop-produced artwork of the original printing, and song titles such as "Plague Bearer", "Dark Millennium", and "Through The Eye Of Terror".
- American Doom Metal band Cirith Ungol released the songs "Chaos Rising" and "Join the Legion" on their 1991 album Paradise Lost.
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