When activated, Joker snaps his fingers, and sends out a small projectile with an explosive area of effect. The projectile doesn't do much damage, but will cause the opponent to become cursed, taking damage over time. It can also be used to start combos in specific situations due to its favorable launch angle.
If Arsene is currently out when the move is used, Joker instead uses Eigaon, a more powerful projectile that hits multiple times, and causes the curse to deal more damage and do so more frequently, but last slightly less time. It will also explode and maintain its multihit hitbox if it hits the floor, allowing it to be used for area control by the player. This is especially helpful if the opponent is on the ledge, although it is a committal option in this situation.
The damage taken from the curse is as follows.
Eiha is a Death element Persona skill first appearing in Revelations: Persona. It and Eigaon serve as Curse element skills in Persona 5. Eiha is the basic form of the attack, while Eigaon is the most powerful single-target form. Notably, Arsene can learn Eiha but cannot normally learn Eigaon; however, Arsene has access to it in the first battle done in the story's prologue and can inherit it from other Personas. Arsene also learns it in the spin-off game Persona Q2: New Cinema Labyrinth.
The lingering damage effect is not present in Persona 5, though it may be a reference to the spell's attributes in Revelations: Persona, where it deals persistent damage to the targeted enemy.