Mongbats

A cross between a monkey and a bat. Mongbats are strong and vicious, attacking their victims with strength and without fear. A large number of these winged anomalies, which had developed in the Underworld, can threaten an experienced group of adventurers.

Mongbats usually dwell only in dungeons, but they are also seen in the wilderness on occasion.

First seen in Ultima V, they stayed the same in all their appearances, although in both Underworlds, Mongbats were stronger to give the player more of a challenge.

Trivia

 * Considering the number of references to the The Wonderful Wizard of Oz throughout the Ultima series, mongbats may be based upon the winged monkeys from the same novel.
 * Mongbats were to be included in the cancelled Ultima X. Link: Ultima X Mongbat