Nightmare.

A black skeleton covered in black liquid, it has one blue eye, while the other is covered with black mucus.

He wears black sneakers with socks, shorts with white stripes, a sweater and a black sweatshirt.

Very aggressive, but at the same time calm. He can keep everything under control. Slightly irritable.

He loves to read books, his favorite genre is a novel. He can play the violin and even some other musical instruments.

quite smart and well-read, he sometimes gets very stuffy

hot strong coffee and apple pie

Dream is the Brother whom he hates. Nightmare hates his brother Dream more than anyone in the world. Killer is a subordinate of Nightmer. Killer must call Nightmare "Boss", otherwise he will feel bad.