Caster (Fate/Zero)

Caster is a character from the Fate/Zero. He is the Servant of Uryuu Ryuunosuke during the 4th Holy Grail War. Caster derives pleasure from first providing his victims with a moment of relief and hope, before killing them in a variety of horrific manners.

Identity
His true identity is, a French nobleman who was once a comrade-in-arms of. He first introduces himself to his Master as, which is the name of a fictional character based on Gille himself.

Role
Caster was summoned shortly before the Fourth Holy Grail War began. His Master was Ryūnosuke Uryū, a serial killer who unwittingly performed a successful summoning ritual using the blood of a murdered family. Like his Master, he is almost devoid of any morality, and has no interest in obtaining the Holy Grail. He enjoys offering his victims brief moments of respite, or even the hope of release or escape, before inflicting death through gruesome and horrific means. According to Caster, allowing his victims hope will amplify the despair and terror upon their moment of death, a fact that he revels in. He is also capable of keeping human beings in stasis with his magic, allowing his master to play with the victims organs as a musical instrument.

Caster initially expresses an interest in Saber, appearing to be familiar with how she came to ruin at the end of her life. In truth, it is because he has mistaken her for Jeanne D'Arc, whom he had been infatuated with when alive. Even after Saber reveals her true identity, Caster continues to delude himself, believing that her memories were warped by the trauma of her death. He even makes plans to capture Saber and force her to remember her 'true' past.

It soon comes to the attention of Kotomine Risei, the Holy Grail War's regulator, that Caster is kidnapping children throughout Fuyuki (for use in his spells and for his Master's amusement), and that he and Uryū lack the discretion practiced by the other Master-Servant pairs. Fearing their actions might compromise Tohsaka Tokiomi's chances of winning the War, Risei suspends all fighting and offers a reward of extra Command Spells to the Master who dispatches Caster and Uryuu.

Using the captured children as hostages, Caster draws Saber out and traps her in battle with his seemingly infinite army of summoned monsters. He is defeated when Lancer intervenes, breaking through the monster horde with Saber's aid, and using Gáe Dearg to disable Prelati's Spellbook and dispel the summoned creatures. An enraged Caster then retreats.

In his second bid to capture Saber, Caster merges a horde of his monsters into an immense, Lovecraftian beast, with himself at its centre. Despite its vast strength and regenerative powers, it is ultimately defeated by Saber, who incinerates the beast with her anti-fortress Noble Phantasm, Excalibur. The light from Excalibur's blast causes Caster to recall memories from his past, before he began his forays into murder and the occult, back when he still served alongside Jeanne D'Arc. This evokes tears and a tinge of regret in Caster, moments before he is destroyed along with his monster.

Abilities
In terms of Servants of the Caster class, Gilles is one of the weakest on record. Possessing very little ability in Magecraft himself most of his power is derived from his Noble Phantasm, Prelati's Spellbook which acts as a massive prana reserve and a guide for whatever spell he hopes to enact. Despite this however, due to the effects of the spellbook he is capable of summoning near endless waves of demonic amphibious familiars without fatigue. Thus making him a viable threat despite his failings. It is noted that he had been a true knight during life, and he could potentially handle classes other than Caster if summoned properly.

While having gone insane during his lifetime, Gilles does still seem to possess some form of intellect, his past experience as a general perhaps aiding in this. He seems to have a warped cunning, convincing his victims of vague hope before brutally murdering them. When hunting Saber he managed to appear ahead of her on the road and lure her into the Einzbern forest, suggesting some form of reasoning and insight.

Finally, while most Caster class servants do not possess great physical strength as other servents and at most can only have a certain level of strength that can exceed that of humans, Gilles may actually best others of his class is in physical power, having in one scene crushed a child's skull completely with seeming ease and smashing holes in the ground and in wall while in anger and frustration. while other casters, such as Medea had trouble facing humans in melee combat. Again this may be owing to his military experience and remarkable physical condition in his past life being greater than his magical powers.