Nightmare is avian, he has black wings, and he is 15 years old along with his twin younger sister Dream, He cares for her a lot, He is quieter and smarter compared to her, and He likes reading books and following where Dream goes, He dislikes humans and other monsters going near her, He knew fully well that they’re trying to take advantage of Dream since she is beautiful and had golden fluffy wings, she also had an aura that could make anyone calm, happy. Nightmare always distracts her from them