Ultimoose is an athletic daredevil moose-like creature with his very own branch of martial arts and originally the Night Master affiliate. Tough as nails, he's a man in the stereotypical meaning of the term, being brash and short sighted with limited intelligence and using third person when speaking of himself. Training and muscle-obsessed with an ego to boot, Ultimoose frequently tends to insult people by calling them "little girls" or "ladies". He sports a pair of mechanical antlers that can transform into a variety of weapons and other devices.
In the episode "Deja Foo", Ultimoose merged with the Night Master and became the Night Mooster, but was reverted back to normal after Yang reversed time and and retrieved the Amnesulet first. As of "Welcome to the Dark Tomorrow", Ultimoose has become affiliated with the League of Evil.
His name is a mash-up of the words "ultimate" and "moose".