Lythoin Cavern Worms were a species of massive worm native to the underground Lythoin Caves of planet Merdegraw. They were huge, bluish green, with a strange maw looking more like pinkish feelers that went around its entire circular mouth. The creature popped out of holes, looking for something to eat. Ratchet could have bashed them with his Wrench, causing them to have to return to their burrow.
- A sapient lifeform similar to this worm is seen in Zordoom Prison in some of the cells.