The True Name of the Heroic Spirit of the Class Card is Hassan-i-Sabbah, summoning one of nineteen wraiths depending on the user. The Hassan-i-Sabbah utilized by Shinji is unnamed. The Hassan is said to have been "an assassin that implanted an evil spirit into their right arm." The description matches that of Hassan of the Cursed Arm, but the abilities and Zabaniya of the Hassan utilized by Shinji differ slightly, with "signs of medical and industrial procedures performed after the spiritual transplant are visible."
Including the Assassin Class Card grants one of the many roped daggers that make up Assassin's arm as a weapon, similar to a whip or a rope dart.
Installing the Assassin Class Card grants the power of Assassin, with blades mounted in the user's feet that are wrapped up until needed. Its main feature is an arm made up of the intertwining roped daggers, which can regenerate and duplicate the daggers as they are a part of the user's body, even bleeding when cut. The arm can be disconnected by the user to act as a decoy, the arm turning into a massive, durable giant of roped blades to draw attention and crush the target with brute force, while the user sneaks behind them in the confusion to strike. It also allows the user to utilize the Assassin's Noble Phantasm, Zabaniya: Dead Heartbeat Melody.