Angra Mainyu

Angra Mainyu serves as the unique Avenger-class Servant for the Einzbern family. While he is not the legendary evil deity from Zoroastrianism, his defeat during the Third Holy Grail War fundamentally changed the ritual. This event corrupted the Grail, turning it into a vessel for All the World's Evils and leaving a permanent scar on the history of the Holy Grail War.