Caster (Fate/Extella)

Caster (キャスター) is a Masterless Caster-class Servant granted with control over the security of the SE.RA.PH in the Moon Cell Holy Grail War. He is an independent Servant in the conflict of Fate/Extella.

Identity
Caster's True Name is, a "celebrated genius in human history." A mathematician ahead of his time.

Appearance

 * Temporary Everyday (一時の日常) - Archimedes's casual costume.

Personality
He favors logic and rationalism, does not stray from his own views if possible, and endeavors to treat all things with objective dignity.

Fate/Extella
The Caster Servant Archimedes appears before Nero, who fights for the two Regalia. Archimedes is a standalone Servant summoned as a maintenance engineer for the Moon Cell Automaton, the spiritronic computer that created the spiritronic virtual world SE.RA.PH. He says that the 14,000-year refresh cycle for the Moon Cell's systems is happening right now. However, he declares that the Regalia, articles of authority, are necessary for the system refresh; they are incomplete, having been divided between Nero and Tamamo-no-Mae in an accident. He renews the determination of Nero and her Master to fight, not just for dominance over territory, but to stabilize the lunar world itself, which has begun to show signs of discord.

Abilities
Caster cannot participate in the Holy Grail War due to his position as head of security, but he can still fight even if he cannot compete for the Holy Grail.

Technique Elucidation (術理解明) is a skill to interpret and restore more or less anything that can be called a formula. Not just repair magecraft, but also damaged circuits and even crests. An esoterica among esoterica even in an age when magecraft still existed. But completely useless in combat.

Aptitude for Slaughter (Tools) (殺戮技巧(道具)) is a skill possessed by Heroic Spirits fitting the Assassin or Berserker classes. Implements used gain damage plus against "humans". A condition that Archimedes has even though he doesn't want it. Like a sort of curse.

His Noble Phantasm is Katoptron Katho Phlegon.

Adjacent Movement
Adjacent Movement (並行移動) -- also referred to as Sliding (スライド) -- is a privilege permitted to Archimedes as a System Administrator of SE.RA.PH, which permits the browsing of Quantum Realities (量子世界), and, within such, the authority to enact transportation (移動権限). A capacity that permits movement between Adjacent Realities (並行世界).

Originally, the capacity permitted only that browsing be conducted. Even within the domain of SE.RA.PH, the projection of the Consciousness (意識) and the direct transportation of the Corpus (肉体) are categorically impossible. Per established record, the Corpus is unable to withstand Temporal Retrogression (時間の逆行) or the bypassing of the Walls of the Worlds (世界附の壁), and collapses if such is attempted. It was the taint (浸食) of the Wandering Star (遊星) that permitted Archimedes and Dark Eliza to do so; in becoming profaned by the Spiritrons (Cells) of the Wandering Star, their Existential Integrity (存在強度) was enhanced.

As in the events of the present work, existences such as Archimedes and Dark Eliza were submitted to record by Moon Cell, Sliding will be prospectively disallowed to them as well. The period of time wherein "he wasn't yet identified as an accomplice to the Wandering Star" was to Archimedes the best opportunity by which to maneuver to as a saboteur -- but even so, his plot came to be foiled.

Incidentally, in the event that Archimedes or Dark Eliza slide into a different world, if there exists a reality similar to World (Route) of destination, their "analogue" in the World of destination is displaced into the similar reality -- merging into the particular existence that is identical to them. If there exists no reality that is similar, a merging into a stronger "self" is enacted.