Nightmare was always bullied his whole life by the other monsters far out into the town whenever they came to only see Dream, he finally got tired of the pain and ate the black apple.

Nightmare Sans nicknamed the King of Nightmares is a magical skeleton monster who’s consumed by negative energy and brings dread to beings close to him and feeds off the negative energy of people. Having a cruel, aggressive, evil, sadistic and sarcastic attitude. And four black tentacles coming out of his back.