Sköll and Hati

Sköll and Hati are the twin wolves that make up Maxine Fujioka's Persona.

Mythology
Sköll and Hati are the twin sons of the wolf Fenrir, who was foretold to kill the god Odin during the events of Ragnarök. Sköll was destined to eternally chase the Sun across the sky, while Hati chased the Moon, in an attempt to eat them. It was said that during Ragnarök, they would finally succeed.

User's True Self
Max's dungeon is a recreation of an old Norse mead hall, possibly even Valhalla itself. Inside, the group must face a horde of skeletal warriors, which could be taken as the souls of those slain in ancient battle and lead to the hall by valkyries. At the end stands the monster Fenrir, who mistakes the group as Odin and his warriors. Fenrir proclaims he will devour Odin and bring about Ragnarök, and the battle to save Max begins.

During Max's acceptance of her inner self, she reveals she secretly wished the whole world would just end, so that all the awful people would finally go away and she didn't have to fight so hard for justice. With the help of her friends, she realizes this isn't the right way to go about changing the world, and vows to work toward the proper kind of progress.

Sköll
When Max uses a Mudo skill, Sköll appears, swallowing the Sun and casting the battlefield in a suffocating shroud of darkness. This darkness seems to have a mind of its own, and attacks enemies while they're incapacitated.

Hati
Alternately, when Max uses a Hama skill, Hati appears, swallowing the Moon and shining a searing light across the battlefield. Enemies caught in this light are burned, and, in the case of one-hit-kills, have the very flesh melted from their bones.