Arsène (アルセーヌ, Arsene), referred to as Arsene prior to Persona 5 Royal, is the initial Persona of Joker in Persona 5. The source of Joker's supernatural abilities, he represents the rebellious side of Joker's soul.
Arsène is the personification of the rebellious side of Joker's soul, expressing righteous indignation for his mistreatment and desiring retribution against those responsible. Personas exist within all people, but without the right catalyst, a person usually goes their whole life unable to learn about their existence. After Joker's friend Ryuji Sakamoto is nearly killed, Arsène is able to make contact with Joker and form a contract with him. From there, he grants Joker his supernatural abilities to combat malevolent forces.
Arsène is based on the literary gentleman thief Arsène Lupin, from a series of novels written by Maurice Leblanc. He was known for targeting criminals or those who were much worse than himself, making him an anti-hero of sorts within his own stories.
In Super Smash Bros. Ultimate
As a moveset element
Main article: Joker (SSBU)
Arsène plays a critical role in Joker's moveset, appearing when his Rebellion Gauge has been filled and upgrading Joker's special moves. When Joker uses Rebel's Guard with a full Rebellion Gauge, Arsène appears. Joker's normal attacks are enhanced with additional hits by Arsène, who is fully intangible to attacks while active. Joker also has longer rolls when he is summoned.
Arsène is fully voiced in Joker's reveal trailer, while during gameplay he will remain silent. This is in-line with Persona 5, where Arsène will talk during a handful of pivotal moments in the story but is otherwise entirely silent, including during battles.
Arsène is included in both of Joker's Fighter Spirits, which can be obtained by completing Classic Mode. They are also available periodically for purchase in the shop for 500 coins, only after Joker himself is downloaded. Unlocking Joker in World of Light allows the player to preview the first spirit below in the Spirit List under the name "???".