A band of Werewolves led by Zevon. They attempted to captured a wizard so that they could add a magic-wielder to their ranks. Even after that they were eventually defeated when Thundarr and Ariel learned how to reverse the transformation. A certain pool's water would cause werewolves to revert if they were immersed in it.
The Werewolves's leader was the only one who could add someone to their ranks. In the end it was discovered the Zevon was originally a Wolf, and that his Lycanthropy caused him to become more human. How Zevon became a werewolf is unknown.