Nightmare, the embodiment of fear, could have a twisted sense of humor, finding joy in the chaos he creates. He could be cunning and manipulative, toying with his opponents before unleashing his full power. And despite his broken nature, he might have a few quirks or hobbies that make him oddly relatable, he is a demon that came straight from hell, and usually takes the form of a tall pitch-black humaniod figure with 4 horns from their head, with 2 glowing eyes similar in the color of fire.