𝕂nightmare

Appearance and abilities
In his current "corrupted" form, Nightmare appears as a skeleton completely covered in a viscous black substance:
Tentacles: Four powerful tentacles grow from his back, which he uses as blades or grabs in combat.
Eye: Only the left eye is visible and glows turquoise; the right eye socket is usually hidden by mucus.
Emotional Manipulation: He is able to sense negativity anywhere in the multiverse and amplify it, driving people to insanity.
Immortality and Protection: The black slime acts as a shield, absorbing physical and magical attacks. It is virtually invulnerable as long as negative emotions persist in the world.
Personality and weaknesses
Personality: Nightmare is cunning, calculating, and well-read (he spent hundreds of years studying the multiverse). He does not tolerate lies and harshly punishes those who break deals.
Weaknesses: His main weakness is positive emotions, which literally weaken and hurt him. He cannot enter worlds filled with pure happiness (such as Haventale). Light can also cause him harm.

Capabilities
Teleportation through darkness.
Change of shape.
Absorbing negative emotions for strength.
Mind manipulation through negativity.
The weapon dissolves into its form.