Servants participating in the Fourth Holy Grail War and their true identities:
- Saber: King Arthur, the same character from Fate/stay night. Known as the King of Knights, she maintains a high code of honour. 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.
- Archer: Gilgamesh, a rogue servant in Fate/stay night, the King of Heroes. He dislikes the presence of Saber and Iskander in particular since they were kings like he was. Much to Tokiomi’s displeasure, Gilgamesh has difficulty acting covertly, especially when his considerable pride is wounded.
- Lancer: Diarmuid Ua Duibhne, a Servant with two Noble Phantasms: Gae Buidhe – Golden Rose of Mortality and Gae Dearg – Crimson Rose of Exorcism, which can counter Saber and Berserker’s abilities. As a knight, he holds a strong sense of honour in battle and loyalty to his master.
- Rider: Iskander (Alexander the Great), the King of Conquerors, who desires to defeat Saber and Lancer in particular. Has several Noble Phantasms, the first of which is Gordius Wheel – Wheel of Heaven’s Authority, which summons an ox-drawn chariot when Iskander slices the air with his sword. His eccentric and overbearing personality along with his incredible abilities creates difficulties for his Master and their opponents.
- Caster: Bluebeard (Gilles de Rais), a Servant who derives pleasure from first providing his victims a moment of relief before terrorizing them and then killing them. Expresses an interest in Saber because he has mistaken her for Jeanne d’Arc, with whom Bluebeard has an infatuation.
- Berserker: Lancelot du Lac (previously known as the Black Knight), 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 mindless, though dangerously skilled, fighter. Despite his insanity, he is still able to instinctively recognize Saber.
- Assassin: The Assassins related to True Assassin from Fate/stay night; Assassin is actually composed of several entities rather than just one. They act as reconnaissance agents for Tokiomi and Kirei after Gilgamesh “kills” one of them.