Gelatinous Cubes

Called 'dungeon-sweeper' by some, the Gelatinous Cube is a subterranean dweller that roams corridors in search of food. Their bodies are composed of a clear, corrosive, jelly-like substance which renders them difficult to see, but they may sometimes be detected by the remnants of armour or debris contained within them. They are omnivores, digesting anything they find after absorbing it into their massive bodies. Contact with a Gelatinous Cube hath ruined the armour of many a hardy warriors.

Found in deeper dungeons.

Lore
''Called 'dungeon-sweeper' by some, the Gelatinous Cube is a subterranean dweller that roams corridors in search of food. Their bodies are composed of a clear, corrosive, jelly-like substance which renders them difficult to see, but they may sometimes be detected by the remnants of armour or debris contained within them. They are omnivores, digesting anything they find after absorbing it into their massive bodies. Contact with a Gelatinous Cube hath -ruined the armour of many a hardy warriors.''

- from "The First Age of Darkness", Ultima I