|Japanese Voice||Satoshi Tsuruoka|
Caster is the Caster Class Servant of Uryu Ryuunosuke in the Fourth Holy Grail War of Fate/Zero. His true identity is Gilles de Rais.
His true identity is Gilles de Rais (ジル・ド・レイ, ?), a French nobleman from the 15th century. He participated in the Hundred Years' War as a Marshal and was once a comrade-in-arms of Joan of Arc. He remembered the time when he and Joan were decorated as saviors and national heroes by King Charles in the cathedral with the ars nova melody playing in the background. In his life time, he admired Joan deeply and he was devastated when she died. His faith in God changed greatly as he saw God abandoning Jeanne. Back in his own territory, he became a mass serial children killer where he murdered and raped children in his neighborhood. "Bluebeard" is the name of a fictional character which is based on Gilles himself and it became the symbol of fear. Gilles came in contact with magecraft through François Prelati who was like a friend and a tutor. Gilles himself also participated in the alchemical and Demon-summoning rituals, but François was the Magus leading the rituals, Gilles was simply the only patron. Unfortunately for Gilles, his
total assets of his lands exceeds the scale of the Duke of Brittany at that time. Which even became a threat towards the king. Gilles finances collapse itself because of his extreme wasteful habit in his private life, it became fearful as he would most likely sell his lands to the enemy country. He continued his atrocities for 8 years until the Church and State caught him, they used this opportunity to confiscate his wealth and land. He was executed for his crimes. After his death, his soul was removed from the cycle of transmigration and stored in the Thrones of Heroes where he became an existence not exactly a proper Heroic spirit.
He has huge, rolling eyes and oily, glistening cheeks. Because he was originally a knight, he has a muscular build and is a very tall individual. He has a huge, thick, navy blue cloak with red stripes on it, and cracks on one of his hands, and usually has a scorn on his face, unless he's having fun torturing and killing people.
Caster is a troubled person, having lost the woman he admired. Like his Master, he is almost devoid of any morality, and has no interest in obtaining the Holy Grail until he meets Saber. 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 Joan of 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.
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.
Before Gilles de Rais was chosen for Fate/Zero. Gen Urobuchi had trouble thinking of a Caster-class Servant for the Fourth Holy Grail War, so he asked Kinoko Nasu if he can use a Chinese Xian. It was when Nasu explained the Western-only rule of the Fuyuki system.
Takashi Takeuchi likes drawing a character with such strong peculiarities.
While he used to be good looking, he comments that Gilles must have "wet his eyebrowless, round, and cute eyes as he was adoring Joan." Urobuchi believes he is more the style of a creature than a Caster, and that he is at his height when he smiles.
Atsuhi Ikariya was in charge of the character design for the anime version.
Caster was summoned shortly before the Fourth Holy Grail War began. His Master was Ryuunosuke Uryuu, a serial killer who unwittingly performed a successful summoning ritual using the blood of a murdered family. Ryuunosuke lacked a cataylst so the Grail chose a servant with the closest personality to Ryuunosuke. He first introduces himself to his Master as Bluebeard.
It soon comes to the attention of Risei Kotomine, 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 Tokiomi Tohsaka'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.
When Caster and Ryuunosuke returned to their lair, they found that their work was destroyed by others. While Ryuunosuke cries, Caster comforts him but to his surprise Ryuunosuke claims that God punished them for having too much fun. Caster is surprised though, when he's asked about the existence of God, as he didn't believe his master to be spiritual. Ryuunosuke then shares his philosophy that God must be somewhat malicious to make the world with them in it, as he believes that God likely enjoys displays of violence, gore and evil actions. This firmly wins Caster over, as he hails Ryuunosuke as a brilliant philosopher and they resolve to perform a grand spectacle to amuse God.
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 Joan of Arc. This evokes tears and a measure of regret in Caster, moments before he is destroyed along with his monster. He was the second servant to die in the Fourth Grail War.
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 mana 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, making him a viable threat despite his failings.
Much like Assassin of the Fifth War, Caster is an aberration in the normal Servant summoning process who
cannot be called a proper Heroic Spirit. He was never actually a practitioner of magecraft during life, and he only funded and participated in alchemical and Demon-summoning rituals lead by the magus François Prelati (フランソワ・プレラーティ, ?) after his sanity was lost. Due to the massive mistakes Ryuunosuke made during the summoning ritual, he was placed into the Caster class container even though he is completely unsuited for it much like "Sasaki Kojirou" was placed into the unsuited Assassin class container. While his occult knowledge is terrifying, it is noted that Gilles has a good body build from his time as a knight, and he could potentially handle classes other than Caster if summoned properly. While he became a general, it can be said his money was his greatest asset rather than his martial prowess.
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.