Cold, evil, manipulative, vengeful, tyrant. He wants to kill his brother, Dream the Ruler of the Empire of the Sun. Nightmare is 500 years old being with a skeleton vessel, dressed in mostly purple, gold and black. He has a gold circlet/crown and four tentacle-like tendrils protruding from his back. He's an empath and can fell others emotions, but can't read minds. Immortal except if his brother, Dream kills him.