During the "Chaos War" storyline, Amatsu-Mikaboshi (now adopting the title of Chaos King) has amassed an army of alien slave gods and is attempting to destroy absolutely everything and become the only being in the Universe once more. He travels to Nightmare's realm while they are trying to torment Hercules with visions of Amatusu-Mikaboshi and quickly defeats the demon. Nightmare attempts to join Amatsu-Mikaboshi's forces but the ancient force of nature doesn't get tricked by his begging and destroys the heart, apparently killing Nightmare. His apparent death is felt by those who have psionic powers and it is later revealed that those who fall asleep enter into a state of berserk rage. Amatsu-Mikaboshi steals Nightmare's powers and minions.