Caster(Gilles de Rais)

Caster is the Caster Class Servant summoned during the fourth Holy Grail War of Fate/Zero by his master Uryu Ryuunosuke. He's later summoned again as Caster during the Sixth Holy Grail War of Fate/Cruelty, ironically by the same master, now over 30 years older than he was previously. He is also one of the Servants summoned by the Protagonist of the Grand Order conflicts in Fate/Grand Order.

Identity
Gilles de Rais