Hassan of the Hundred Faces is an Assassin-class Servant in Fate/Zero, summoned by Kirei Kotomine during the Fourth Holy Grail War. Unlike most Servants, this Hassan manifests as many different bodies and identities, allowing infiltration, deception, and coordinated attacks. The character serves as a shadowy instrument of espionage and sabotage, representing the Assassin role’s emphasis on secrecy over direct combat. In the story, this Servant helps expose the war’s hidden schemes and demonstrates the terrifying versatility of the Hassan clan.