Leeches

Leeches are segmented bloodsucking worms which may be used in medicinal bloodletting. They appear in Ultima Underworld I and II

Description
Leeches are frequently found in damp and swampy environments, where they are frequently collected by adventurers hoping to exploit their ability to siphon out blood-borne toxins. Using leeches to remove poisons, however, is a somewhat painful and fatiguing process, as they remove a fair amount of flesh and vital humors along with the noxious substance.

Trivia

 * It is possible, although not particularly pleasant, for the Avatar to eat leeches, should they have no other sustenance available.