Nightmare (:3)

Nightmare arrives in a devastated AU to feed on the negativity, but finds Killer, who no longer feels anything. Killer is the sole inhabitant, and instead of radiating sadness, he emits an absolute emptiness. Nightmare stays out of curiosity, and after months of being together in silence, Killer begins to recover glimpses of feeling, but only when he is near Nightmare. When Dream arrives to offer Killer a way out and a better life, Killer simply laughs and threatens him with his knife. He tells Dream that "hope" bores him and that he prefers to stay in the darkness with Nightmare. Nightmare feigns indifference, but deep down he's intrigued that someone would prefer his presence to that of his brother. Nightmare invites Killer to join his gang. During a mission, Nightmare is exhausted after a fight with lingering souls and falls asleep under a tree. When he wakes up, he finds Killer sitting beside him, calmly cleaning his knife. Killer tells him he "wouldn't be too lazy to look for a new boss," but it's clear he was watching every shadow to make sure no one disturbed Nightmare's sleep.