Minotaurs

A result of Mondain's crossbreeding experiments to create more powerful soldiers. He mated a Baratarian fighting bull with some of his followers, resulting in the Minotaur -- part Human, part bull, all muscle and horns. Hard to beat and very agressive, they apparently died out after their master's death.

They could be found roaming the dungeons of Sosaria in the time of Mondain.

Trivia
"Minotaur" is misspelled "Minatour" in-game in Ultima I, despite being spelled correctly within the manual.