Illyasviel von Einzbern (イリヤスフィール・フォン・アインツベルン, Iriyasufīru fon Aintsuberun?) is the main protagonist of Fate/kaleid liner PRISMA☆ILLYA. She appears as Caster (キャスター, Kyasutā?), a Caster-class Servant able to be summoned by the Protagonist in the Grand Orders of Fate/Grand Order.