|“||The haunted mansion that's shrouded in darkness is the perfect home for the Gruegloom. Grueglooms cluster together and try to consume you. So when they surround you, stay in the light!”|
|— Daroach • Kirby Mass Attack|
Gruegloom is a skull that is disguised as a dark purple or blue cloud with menacing eyes and a big mouth with fangs.
Gruegloom appears exclusively in Stage 6 of Volcano Valley. It appears in dark areas inside Shadowbite's mansion. As shown in an in-game cutscene, it enjoys eating small creatures such as Beanbons and pursues any Kirbys it finds. If Gruegloom gets close enough, it devours the Kirby, instantly KOing him. Once eaten, the Kirby cannot be brought back. If Gruegloom has light shined on it, it turns into its true form and panics. It is vulnerable in this form and can be defeated easily.
Blue Gruegloom does not move and cannot be defeated, but disappears when exposed to light. It colonizes with many other blue Grueglooms, filling a hallway in the mansion. To get through, the Kirbys must stay inside the light cast by a moving ceiling lamp.
- Gruegloom is likely based on the grue, a monster from the Zork series of computer games. Like the Gruegloom, grues inhabit dark environments, can instantly defeat the player by eating them and are weak to light. As with the different types of Grueglooms, the effects of light on grues can vary from game to game, either causing them intense pain or making them spontaneously combust.