Avenger (Fate/Zero)

Avenger (アヴェンジャー) an Avenger-class Servant who appears in the Fourth Holy Grail War of Fate/Zero and in the Grand Orders of Fate/Grand Order.

Identity
Avenger's True Name is Black Iri, formed through Angra Mainyu possessing the remnants of Irisviel von Einzbern's personality in the Greater Grail.