Kirei Kotomine (言峰 綺礼, Kotomine Kirei?) is the main antagonist of Fate/Zero and Fate/stay night. He acts as the Master of Assassin during the Fourth Holy Grail War, but then later forms a contract with Gilgamesh after Assassin's defeat. Their contract lasts into the Fifth Holy Grail War, where he also deals a fatal wound to Bazett Fraga McRemitz to seize control of her Servant, Lancer. While he is an ordinary Master during the Fourth War, he acts as the supposedly impartial mediator during the Fifth War.