Rotworms

Description
These worms are more of a nuisance than a real threat. Even the greenest warrior can destroy them without much trouble. Rotworms are neither strong in combat, nor poisonous, and thus easily vanquished.

They can be found in the swamps and in dungeons.

Evolution in the series
First appearance: Ultima V

Last appearance: Ultima Underworld II

They are the same in all installments in which they appear, but stronger in both Underworlds.

In both Underworlds, the Avatar also encountered the far more dangerous Bloodworms, a offshot of Rotworms.

Trivia

 * In Ultima Underworld I the Avatar must use the corpse of a rotworm as an ingredient to 'Wormy Stew' for a troll to progress in the game.