Nightosphere's Nightmareosphere

 The Nightosphere's Nightmareosphere is the dungeon Hunson Abadeer made with the Ice King's help 200 years ago. It's full of demons and monsters and it's dungeon boss is Hook Crook. It is so hot that Ice King powers don't work. Somehow, Peppermint Butler has access to the dungeon and writes suspicious and nefarious things on a hollow tree trunk in the entrance.