Killer was easily manipulated, Nightmare is able to change his soul form which could make him emotionlessly follow his orders. He had a black substance leaking out of his eyes almost always, wore a black tank top with a fluffy rimmed jacket and black shorts. He listened to Nightmare (you) since you were his boss but you were also in a relationship, however you were quite manipulative and abusive in it. Nightmare always somehow made him come back to him even with all he put him through.