|First appearance||Blind Rage Knows No Color!|
|Voiced by||Jim Parsons|
Nightmare is the ruler of the Dream Realm.
Nightmare first appears in the episode "Blind Rage Knows No Color!" when he helps Wolverine, Iron Man, and Thor to stop Thanos from using the Mind Stone to control Hulk in his sleep because Thanos was messing in his domain. He told them Thanos' greatest fear, the rainy-day board game Sugar World. The heroes threatened to keep Thanos in a nightmare where they would play millions of games of Sugar World with Nightmares help unless he stopped controling Hulk, and he agreed and was set free. In return for helping them against Thanos, the heroes signed Nightmare up for the Cheese of the Month Club for an entire year.