A thin, wiry man dressed in black sackcloth and leather and wearing a white skull mask. His right arm is wrapped in a series of leather straps and bound up, making it useless in normal combat.
As with every Holy Grail War except the Fifth, Assassin’s true identity is Hassan-i-Sabbah, the founder of the Hashshashin order. His abilities are different in every war however, due to the head of the order at any given time always being known as “The Old Man in the Mountain” despite who he or she might actually be. His Noble Phantasm is known as Zabaniya, but the form it takes differs with each incarnation.