The Master of Saber and the main protagonist. Born in Fuyuki City, Kiritsugu was raised on Alimango Island, where he lived with his father, Norikata Emiya, the fourth family head of the Emiya family and a magus specializing in time magic. He became friends with Norikata's assistant, a local girl called Shirley who was four years older than him, developing a crush on her. However, disaster struck when Shirley became a vampire after drinking one of Noritaka's potions. She pled for Kiritsugu to kill her, but he fled instead. Shirley subsequently lost control and turned all the residents of Alimango Island into vampires.
Their village was soon overrun by Executors from the Church and Enforcers from the Mages' Association, agents whose purpose was to destroy all the vampires and eliminate any trace of civilization and vampirism on the island respectively. Kiritsugu was the only survivor of the 'cleansing', saved by Natalia Kaminski, a freelance Enforcer who wanted information on the magus responsible. Returning to the hidden Emiya residence, Kiritsugu confronted his father on his research and Shirley's death. Upon discovering that Noritaka had anticipated such an outcome all along and was making preparations for both of them to flee, Kiritsugu shot him with a pistol.
Realizing that the tragedies he saw in his childhood were common occurrences in the world, the teenage Kiritsugu became a freelancer like Natalia to hunt down heretical magi around the world. Natalia trained him not only in Magecraft, but in tracking, assassination, and all types of weaponry. During a mission on board an Airbus A300 jumbo jet, Natalia was trapped on the plane along with magical bees capable of spreading vampirism and hundreds of infected passengers. Kiritsugu shot the plane down before it could land to contain the vampirism, sacrificing Natalia in the process, who at that point had become like a mother to Kiritsugu. It was then that he became disillusioned with the ideal of becoming a 'hero of justice', as he realized it was impossible to save one person without losing another.
Around eleven years before the fourth Holy Grail War, he took on a child soldier he had rescued as his apprentice, who he eventually named Maiya Hisau, training her in much the same way Natalia trained him. Two years later, Kiritsugu was hired by the Einzbern family to be their representative in the coming conflict. Believing that the Holy Grail could grant his wish for world peace, he left behind his former work. Despite being the true Master of the Einzbern, Kiritsugu operates mostly in the background during the conflict, ambushing other Masters when they are otherwise occupied, while Saber is partnered with Irisviel and made to act out in the open. This is to avoid conflict between Kiritsugu and Saber, as the methodologies of the two conflict with each other too much.
Kiritsugu employs an unusual strategy of exploiting a magus' weak point using technology, utilizing a specialized gun, the Thompson Contender for that purpose. This gun serves as his Mystic Code, a magus' primary tool and trump card. It is used in conjunction with sixty-six Origin Bullets (起源弾,kigendan?), magical bullets created from his first and second ribs on both sides being cut off, extracted from his body, ground into dust, condensed with a craft to preserve his soul, and sealed within bullets as their core. When fired at a magus utilizing magecraft, they cause extreme, usually fatal damage, in addition to preventing the magus from ever utilizing magecraft again.
Irisviel von Einzbern (アイリスフィール・フォン・アインツベルン,Airisufīru fon Aintsuberun?) is the main heroine of the story and Kiritsugu's wife. She is a homunculus prototype created by the Einzbern family with the idea of giving birth to an ultimate homunculus. Like many of the Einzberns, she is skilled in alchemy. Irisviel serves as Saber's proxy Master, since Kiritsugu believes that he and Saber are incompatible. Due to possessing the inborn knowledge and reasoning of homunculi, hindsights gleaned from the 1000 years of history of the Einzbern as well only having nine years of life-experience, she has both the elegance of a lady and the innocence of a child. Her true purpose in the War is as the vessel of the Holy Grail itself. When six or more Servants are killed, she will manifest the Grail, losing her humanity and sense of self in the process.
Created by Jubstacheit von Einzbern, the eighth head of the Einzbern family, she originally saw herself only as a tool to summon the Holy Grail. Upon first contact with Irisviel in the Einzbern residence in Germany, Kiritsugu noted that she had no instinct for self-preservation and expressed doubts about Irisviel's suitability as the Grail to Jubstacheit. In response, Jubstacheit threw Irisviel into a junkyard for rejected homunculi, a dangerous place filled with monsters and spirits, reasoning that if Irisviel could not even survive a night there alone, he would accept Kiritsugu's criticism and furnish him a new homunculi. In response, Kiritsugu rescued Irisviel and decided to give her a sense of self-preservation by personally educating her and teaching her what it meant to be a human. Eventually, they fell in love with each other. Wanting to show Kiritsugu that there could be a future for them after her fated death, she bears Kiritsugu a daughter, Illyasviel von Einzbern. They live together for nine years in total before departing to Japan for the War.
While approving of Kiritsugu's ideal and willing to sacrifice herself for its sake, she does not truly understand that ideal, but only wishes to walk the same path as her beloved. However, in order not to burden Kiritsugu, she decides to behave as a woman who would die for that same ideal rather than a woman that would die for her husband. Her Magecraft involves the creation and forging of matter, as well as its applications. In terms of magical ability, she is stronger than Kiritsugu. Her weapons are thin, long and flexible wires, which she uses to produce an instantaneous homunculus with alchemy that attacks the enemy while changing itself into numerous shapes. She may also use her weapon to immobilize her target.
Saber (セイバー,Seibā?) is the same character from Fate/stay night, the Servant who was summoned by Shirou Emiya. Known as the King of Knights, Arturia Pendragon(アルトリア,Arutoria?), who obtained the magical "Sword in the Stone", she maintains a high code of honour. Stunned to discover that the legendary King Arthur is a young woman, Kiritsugu refused to speak to her directly since her summoning, which Saber initially believes is because he believes the fact that she is a woman makes her inadequate. However, Irisviel later suggests Kiritsugu's anger towards Saber is out of the belief that he could not accept the decisions Saber made or allowed to be made in life yet he could not justify his reasons for why he believed she was wrong.
Though she and Kiritsugu are Servant and Master seeking the same ultimate goal of peace, their differing ideological perspectives result in a strained relationship where Kiritsugu does not directly acknowledge Saber. Believing the cause of the downfall of Britain to be her ineffective leadership, her reason for seeking the Grail is wish for someone else more suitable and effective to lead Britain in her stead. This wish brings her into conflict with her fellow kings Archer and Rider, the former seeking to defeat her to revel in her despair of having her dreams shattered and the latter seeking to defeat her to convince her of the futility and absurdity of her goal.
She possesses three Noble Phantasms, the first of which is Excalibur: The Sword of Promised Victory(約束された勝利の剣（エクスカリバー）,Ekusukaribā?), which can generate a wave of destructive light from the tip when swung, capable of incinerating a large area. The second of her Noble Phantasms, Invisible Air: Bounded Field of the Wind King(風王結界（インビジブル・エア）,Inbijiburu Ea?), is a barrier of wind which sheaths Excalibur and renders it invisible, making it hard for opponents to judge their distance and concealing Excalibur's identity. Her third Noble Phantasm is Avalon: The Everdistant Utopia(全て遠き理想郷（アヴァロン）,Avaron?), the true sheath of Excalibur which provides limited immortality through constant regeneration, automatic healing of wounds and the ability to deflect any attack when activated.
Kirei Kotomine(言峰 綺礼,Kotomine Kirei?) is the Master of Assassin. Before the Fourth Holy Grail War, Kirei served as a priest under his father, Risei Kotomine. Although Kirei understood the distinction between good and evil, he could only revel in committing sins. Hounded by guilt and sorrow and with no alternative, Kirei prayed that, through marriage to a woman he loved, he could finally achieve respite from his tortured existence. When Kirei discovered marriage could not change him, he was on the brink of suicide; his ill wife, filled with concern, committed suicide to show to Kirei that he could still feel compassion for others. However, after her death, Kirei was disgusted to realize he would have preferred killing her instead; from that day on, he ceased pursuing salvation altogether.
Sometime later, he would become the apprentice of Tokiomi Tōsaka due to the wishes of his father, who wished to see Tokiomi obtain the Holy Grail. He participates in the War as a Master under Tokiomi's orders, serving as reconnaissance and support. While researching into the background of the enemy Masters, he sees his own emptiness mirrored in Kiritsugu, and begins to feel a compulsive hatred for him. Conversely, Kirei is the only Master that Kiritsugu fears, the latter seeing him as the biggest threat to his own victory. During the later stages of the War, after goading from Archer, he accepts his own twisted inner nature and murders Tokiomi, becoming the Master of Archer and assuming the role of the main antagonist. Not having a true wish for the Grail, he continues to fight to discover his purpose in life.
Tokiomi is the father of Rin Tōsaka and Sakura Matō, Master of Archer, and an arrogant and manipulative mage. He arranges for Kirei Kotomine to be his understudy in magic and his support in the Holy Grail War. He thinks highly of Kotomine and has him serve in all manners of affairs, appointing him as Rin's guardian should trouble befall him. He is skilled in fire manipulation, and employs a large ruby set in the end of a staff as his Mystic Code to help him shape and control flame. While a skilled magus and confident in his abilities, he considers himself as inferior in potential to Rin and Sakura, who were both recognized by Tokiomi as possessing extraordinary abilities from birth.
Aoi is the mother of Rin Tōsaka and Sakura Matō as well as the childhood friend of Kariya Matō. Though she is devastated by Tokiomi's decision to adopt away Sakura, she quietly accepts the decision as the wife of a mage.
Risei is Kirei Kotomine's 80 year old father, a priest in the Church and the regulator of the 4th Holy Grail War. He is a friend of Tokiomi Tōsaka and actively supports him. While he is proud of his son, who has demonstrated himself to be a perfect heir, Risei fails to understand Kirei in any sense.
The Master of Rider and future Lord El-Melloi II, Waver steals his teacher's artifact early on and uses it to summon Rider. He plans to use the Grail to force the Magus Association to recognize his genius. Despite his difficulties with Rider's overbearing nature, Waver and his Servant form a strong relationship. Though lacking in practical experience in the field of fighting in a war, Waver, mostly in part due to his Servant, survives the Holy Grail War with little detriment to himself and develops a greater sense of perspective of the world.
Maiya is an assistant to Kiritsugu Emiya, a woman armed with a Steyr AUG. She is cold and professional, which makes it easier for Kiritsugu to act as he needs to. Maiya was originally a child soldier from a war-torn land who was rescued by Kiritsugu who taught her his way of life. Her real name is unknown; her current name was given to her by Kiritsugu when he first created false identity documents for her. Despite initial discomfort between them, she and Irisviel develop a mutual respect for one another out of their steadfast dedication to protect Kiritsugu. Maiya also extends her unquestioning loyalty to Irisviel as well.
A freelance mercenary who sold information concerning Noritaka Emiya and his research on vampires. She rescues a young Kiritsugu after the latter kills his father and takes him as her apprentice. During her last mission, she is able to successfully kill a magus that could turn humans into ghouls through magic, but is killed when Kiritsugu shoots down the plane she is on to prevent the infected passengers from killing others when the plane landed. Kiritsugu's last words to her reveal that he viewed her as his mother.
Kariya is the uncle of Shinji Matō and Master of Berserker. He is the only member of the Matō family who truly loves Sakura Matō like a daughter, and is upset that Tokiomi allowed his younger child to be adopted by Zōken. Kariya had previously left the Matō family ten years prior to the 4th Holy Grail War out of disgust for his own family, but returns and makes a deal with Zōken Matō that he will win the Grail War in exchange for Sakura's freedom. Due to his lack of formal training, Kariya was implanted with the same magical worms as Sakura. This caused a number of side effects as the worms would literally eat away at their host, causing Kariya's health to progressively fail in return for significantly expanding his magic circuits and magical potential. By the time of his summoning of a Servant, Kariya's hair had turned white and the nerves on the left side of his face were dead. In addition, his natural lifespan had been shortened to such an extent that Zōken estimated he would only live on for one additional year. However, despite the Crest Worms and his own accelerated training, Kariya remained severely lacking as a Magus. At Zōken's behest, he compensated for this by summoning the most powerful of the seven Servant classes, the Servant of Mad Enhancement, Berserker. However, the high volume of magical energy required to maintain Berserker causes him constant, excruciating pain.
Ryūnosuke is the Master of Caster and a sociopathic serial killer who summons Caster after murdering a family and using their blood as a component in the summoning ritual. He does not seek the Holy Grail, but follows Caster in order to find new thrilling ways to kill people and relieve his boredom.
The Master of Lancer, Kayneth is a nobleman from the Magus Association, Lord of the house of El-Melloi and a prodigy at magecraft. His artifact is stolen by his pupil, Waver Velvet, but he manages to obtain another artifact and summon Lancer instead. While he holds the command spells for Lancer, the energy to materialize the Servant is maintained by Sola-Ui. He is confident in his abilities and takes pride in his heritage, but finds the extent of Kiritsugu's untraditional and underhanded tactics both offensive and unexpectedly challenging to overcome.
The daughter of the head of the spiritual evocation division, Sola-Ui is engaged to Kayneth as a result of a strategic marriage arrangement and the decision of her family to entrust their crest to her brother instead. However, she is coldhearted and does not reciprocate Kayneth's love for her; instead, she becomes infatuated with Lancer, who in turn does not reciprocate her feelings and regards her only as his Master's wife.
Zōken is a shrewd, powerful, and ancient sorcerer and patriarch of the Matō family. He was one of the original three Magi to propose the Holy Grail system, being the designer of the Command Seals, and keeps himself alive by use of worm familiars. Having amassed a large and extensive library of sorcery knowledge, his lessons are strict and harsh, often inflicting a heavy toll on the body. To conceal his status at the ancestor to the Matō family, he masquerades as a relative to his descendants; as such, he is Kariya's "uncle", and Shinji Matō's "grandfather," and adoptive grandfather of Sakura Matō. Because the Matō blood had thinned and no longer produced heirs naturally capable of sorcery, Shinji was incapable of becoming a true sorcerer. Thus, Zōken offered to adopt Sakura Tōsaka into the Matō when her father, Tokiomi, decided to train only his older daughter Rin to become his sole successor.
Disappointed with the lack of sorcerous potential in Shinji and Byakuya, Shinji's father, Zōken blames Kariya for allowing the Matō's magical lineage decline since Kariya, despite being the first in many generations to be naturally capable of sorcery, left the family ten years before the start of the War. Kariya later returns and formulates a deal with Zōken where should Kariya obtain the Holy Grail, Zōken must allow Sakura to return to her family. Zōken does not truly believe that Kariya has what it takes to win the War, and only accepts out of a whim and the small possibility of success.
Archer is Gilgamesh, the same rogue servant in Fate/stay night, the King of Heroes. He takes great pride in claiming to be the first 'hero' ever to set foot on Earth. He dislikes the presence of Saber and Rider in particular since they were kings like he was. Much to Tokiomi's displeasure, Gilgamesh has difficulty acting covertly or regaining his temper when his considerable pride is wounded. He is unique in that he possesses a very large number of Noble Phantasms, but only three are unique to him.
His first unique Noble Phantasm, Gate of Babylon: The King's Treasure(王の財宝（ゲート・オブ・バビロン）,Gēto Obu Babiron?) is a key-shaped sword which opens a rift in space to a mystical vault that holds countless prototypes of Noble Phantasms within. Archer can either draw them out for close combat or fire them out of the rift like bullets. The rift also contains assorted artifacts such as "the wine of kings" and a flying spacecraft from Sanskrit mythology, the Vimana. His second Noble Phantasm, Enkidu: Chains of Heaven(天の鎖（エルキドゥ）,Erukidu?), is an anti-divine chain that binds enemies and becomes stronger the more divinity the target holds. His last unique Noble Phantasm, Enuma Elish: The Star of Creation that Split Heaven and Earth(天地乖離す開闢の星（エヌマエリシュ）,Enuma Erishu?), is the attack generated by his drill-shaped sword, Ea: Sword of Rupture(乖離剣（エア）,Ea?). When its true power is activated, it manifests itself as a massive rip in space-time, possessing unsurpassed attack power sufficient to damage and disintegrate the world itself.
The First of the Knights of Fianna, Lancer possesses a love spot on his face, which causes females with insufficient magic resistance to fall in love with him should they gaze upon it. As a knight, he holds a strong sense of honour in battle and loyalty to his master. Despite being enemies, he and Saber share mutual respect for each other.
Lancer possesses two Noble Phantasms: Gae Buidhe: The Golden Rose of Mortality(必滅の黄薔薇（ゲイ・ボウ）,Gei Bō?), a short yellow spear which inflicts wounds that do not heal as long as the spear exists in the world, and Gae Dearg: The Crimson Rose of Exorcism(破魔の紅薔薇（ゲイ・ジャルグ）,Gei Jarugu?), a long red spear which cancels mana upon contact, ignoring all magical defences and temporarily dispelling all magical attributes of the target struck.
Rider's identity is Iskander, the King of Conquerors, famous in history as Alexander the Great, who desires to defeat Saber in particular because he believes her ideals regarding kingship are delusional and that she would thrive as one of his followers. He derives his status as Rider from a set of divine bulls and chariot purportedly a gift from Zeus, known as Gordius Wheel: Wheel of Heaven's Authority(神威の車輪（ゴルディアス・ホイール）,Gorudiasu Hoīru?), summoned when Iskander slices the air with his Sword of the Kupriotes(キュプリオトの剣,Kyupurioto no Ken?). His eccentric and overbearing personality along with his incredible abilities creates difficulties for his Master and their opponents. He is notably the only Servant that Gilgamesh truly respects as an equal, the latter inviting him to challenge him in combat as many times as he wished.
His first Noble Phantasm is Via Expugnatio: Distant Trampling Domination(遙かなる蹂躙制覇（ヴィア・エクスプグナティオ）,Via Ekusupugunatio?), the trampling attack used by the Gordius Wheel, which causes lightning strikes upon movement, inflicting massive damage to whatever is in its path. His second and most powerful Noble Phantasm is Ionioi Hetairoi: Army of the King(王の軍勢（アイオニオン・ヘタイロイ）,Aionion Hetairoi?), which is a Reality Marble, a self-contained miniature world that contains thousands of the most trusted of his soldiers who fought alongside him in life resurrected as temporary Servants, marching upon an endless plain of sand.
Commonly known as Bluebeard, his real name is Gilles de Rais - a mass serial killer who seems to favour killing children in particular. Caster is a sadistic and evil Servant who derives pleasure from first providing his victims a moment of relief before terrorizing them and then killing them. He expresses an obsessive interest in Saber because he has mistaken her for Jeanne d'Arc, with whom Bluebeard has an infatuation.
His sole Noble Phantasm is Prelati's Spellbook: Text of the Sunken Spiraled City(螺湮城教本（プレラーティーズ・スペルブック）,Purerātīzu Superubuku?), a magical tome made from human skin which acts as a massive mana source and a guidebook for various spells of varying power, with the strongest spell capable of summoning otherworldly, self-regenerating monsters. The strength of his Noble Phantasm helps make up for his otherwise average ability in magecraft.
Previously known as the Black Knight, Berserker is a Servant who possesses the ability to use practically any object as a Noble Phantasm, allowing him to match Gilgamesh in combat. His madness has reduced him to a mindless, though dangerously skilled, fighter. Despite his insanity, he is still able to instinctively recognize Saber. When Saber finally learns Berserker's true identity, she is devastated that her decisions in life and her adherence to chivalry had caused her friend such suffering even after dying.
He possesses three Noble Phantasms, the first of which is For Someone's Glory: Not For One's Own Glory(己が栄光の為でなく（フォー・サムワンズ・グロウリー）,Fō Samuwanzu Gurōrī?), which envelopes him in a black fog that makes his outline blurred and his status unreadable to other Masters. By use of a Command Spell, it is possible to use the fog to allow Berserker to mimic another's appearance, although it is noted that had Lancelot been summoned under a different Class, he would be able to freely disguise at will. Knight of Honor: A Knight Does Not Die with Empty Hands(騎士は徒手にて死せず（ナイト・オブ・オーナー）,Naito Obu Ōnā?), allows him to turn anything he recognizes as a weapon, into a D- ranked Noble Phantasm. If he grabs hold of others' Noble Phantasms, he claims them temporarily as his own and their original rank is retained. His last Noble Phantasm, Arondight: The Unfading Light of the Lake(無毀なる湖光（アロンダイト）,Arondaito?) is a magical sword which, when drawn, dispels For Someone's Glory and Knight of Honour, boosts all his parameters and grants him additional prowess against beings with a 'dragon' attribute such as this war's Saber.
Assassin is actually the reincarnation of the head of the Assassin Order. While every Assassin in every Grail War thus recorded has shared the same name of Hassan-i Sabbāh, they are different persons as all the leaders of the Assassin Order changed their names to Hassan-i Sabbāh upon ascending to the position.
The Hassan-i Sabbāh in the Fourth War became head by intentionally fracturing his psyche during life to confuse opponents, a form of self-inflicted dissociative identity disorder. When summoned as a Servant, this ability manifests itself as the Noble Phantasm Zabaniya: Delusional Illusion(妄想幻像（ザバーニーヤ）,Zabānīya?), which splits his body into up to eighty different entities, sharing his spiritual potential amongst them. They act as reconnaissance agents for Tokiomi and Kirei after Gilgamesh "kills" one of them. Assassin can only be truly defeated if all of them are killed.
^Fate/Zero, Volume 1, Prologue III: One Year Ago
The aberrant entry in the family register said he was the brother of Kariya's father. But even at his great-grandfather, his ancestor at the third generation, there were records of the old man named Zōken in the family tree. There was no way to figure out for how many generations this man came to reign over the Matō family.