The Gem Cave Creature appears as a gigantic brittle star, with a massive disk and short arms. The upper portion of it's disk appears as a giant mound of turquoise colored crystals with multiple geometric facets. The lower half of the disk is colored dark turquoise. The arms are joined near the middle of the disk and taper to a point outwards, they are of a darker shade of turquoise. The ventral side of the disk contains a drill-like apparatus that can unfurl to reveal five turquoise colored arm, and appears to have fingers, that surround a mouth. The dorsal side of the disk houses multiple Drill Parasites that furl themselves to form spike-like protuberance that the Gem Cave Creature can launch.
The Gem Cave Creature has the ability to burrow underground by using the drill underneath it's disk. It can unfurl it's drill to produce five more arms to enhance it's fighting capabilities. It's arms also have the ability to stretch to great lengths as seen when it was fighting Garnet. It's body is presumably durable enough from attacks as Garnet had to get close to it and hit it's weakest point which was it's mouth. It can also launch multiple spikes from it's disk which can unfurl and become Drill Parasites that can aid it in battle.
The Gems were seen being attacked by the cave creature, which Garnet managed to defeat and proceed to take it's gem.
- It was revealed in the episode "Ocean Gem" that monsters that left behind gems upon defeat were previously humanoid Gems that became corrupted in some manner.
- The Gem Cave Creature resembles Brittle Stars more than a Starfish.
- Brittle Stars (Ophiuroids) resemble true Starfishes/Sea Stars (Asteroids) but the main difference is that brittle stars have a distinct central disc and five radiating slender, highly flexible arms. The arms are solid and not hollow like the sea stars, whose central disk and arms are inconspicuously parted.