A gelatinous cube, also known as an athcoid, is a transparent ooze composed of mindless, gelatinous matter in the shape of a cube or rhombohedron.
Typically, a gelatinous cube measures between 10 to 15 feet on a side and weighes as much as 50,000 pounds, although legends exist of much larger cubes. The creature is completely transparent, with only a glint of its surface in the light to give away its position. The occasional random object floating in a well fed gelatinous cube's body could also serve as a warning.
Gelatinous cube bodies are remarkably moldable. They can flow around objects and through narrow passages, quickly returning to their shapes once enough space is available.
A gelatinous cube is a mindless predator that silently roams ancient crypts and vaults in regular, predictable patterns. As they travel the halls of old ruins, they absorb any material in their paths from the floors and walls. Although incapable of climbing walls, particularly large gelatinous cubes could likely also absorb mold and moss from ceilings. Organic material is quickly dissolved in the acidic ooze that makes up the cube's body, while bones and inorganic matter spend some time floating within the creature until eventually expelled. As they slide through the corridors, they leave behind a perfectly clean path, except for an occasional slimy trail.
They cannot see or hear, but were capable of sensing vibrations and were attracted to warmth. When facing an opponent, a gelatinous cube can slam it with an acidic pseudopod or attempt to engulf it. It is possible, although difficult, for sufficiently strong creatures to escape engulfment by a gelatinous cube. Despite their slow speed, gelatinous cubes are strong and can easily push back and knock over even large creatures.
When touching a creature, gelatinous cubes secret a gummy paralyzing substance that is immediately absorbed through the skin into the victim's bloodstream. After successfully engulfing a victim, the cube moves pockets of an acidic digestive substance towards the victim's body, quickly digesting it. Survivors of gelatinous cube attacks often display scars that resemble partially melted wax.
