Atrum Galliasta (アトラム・ガリアスタ, Atoramu Gariasuta?) is the Card User of Caster in the Fifth Ainsworth Holy Grail War. After dying, he has been placed in a Doll body in order to participate in the Holy Grail War.
There is not much known about this version of Atrum and it is unknown when he did die. After being brought back to life, the Ainsworth family gave him the Caster Class Card to stop Shirou Emiya who had entered the War with the goal of stopping the Ainsworths and saving Miyu.
When he installs the Caster Class Card, he wears the cloak of Caster from the Fate/stay night series, with his left leg sticking out of a split in a thicker version of Caster's purple dress, showing that he wears a heavy pale robe underneath that gives him a small asymmetrical apperance.
This Atrum seemingly possesses a sense of invincibility, as shown when he chose to not install until his opponent was directly in front of him, and considered his defeat at Shirou's hands to be "impossible" before dying.
Fate/kaleid liner PRISMA☆ILLYAEdit
In Fate/kaleid liner PRISMA☆ILLYA Oath of Snow, the consciousness of Atrum was brought back from death and was implanted in a Doll body, becoming the Card User of Caster during the Fifth Ainsworth Holy Grail War. Being found by Shirou Emiya at the Ryuudou Temple, he engages a fight with him. He is killed in mid-air by an arrow shot while distracted trying to destroy multiple, thrown projections of Shirou's Kanshou and Bakuya.