A Servant summoned by Caster. Assassin's movement is confined only to within the gate of the Ryūdōji Temple, so as such he is usually represented by a cardboard cutout Caster carries around to stand in for him. However, he manages to finally leave the temple during the Holy Grail Grand Prix, via the loophole of carrying the gate around with him aboard a truck. Due to having been trapped in one location for so long, Assassin has gone crazy and holds conversations with the inanimate gate, treating it like a loyal friend.