Mu (Monster Rancher)
Mu was an extremely powerful monster created by Ancient scientists for a long-ago war in the alternate world of the Monster Rancher game. Mu's creators could not control him, and he created legions with his ability to transform good monsters into his evil servants. They created a second monster, the Phoenix, to defeat him. The two monsters fought each other to a standstill, until the scientists managed to use a fearsome weapon to separate both Mu and the Phoenix from their bodies. Mu's mind remained imprisoned in his castle, along with the Mystery Disks containing many of his old troops.
Centuries later, Holly's father went in search of the Phoenix without the aid of the Magic Stone, but found Mu's castle instead. When he found Mu's disembodied mind, it merged with Holly's father, creating Mu anew. With his incredible powers, as well as being a fearsome combatant, Mu terrorized his world. A brave king once sent his armies to destroy Mu, but none returned.
Mu has recently been opposed only by Genki and his friends, and currently seeks to regain his old body and powers. Mu's four most fearsome servants were known as the Big Bad Four, and consisted of Pixie, Gali, Gray Wolf and Naga.
Mu's name was transliterated as Moo in the American dub of Monster Rancher.