Myuu was apparently a native M-2 resident who, after meeting the King Tuffle's parasitic clone in Age 740, had managed to convert himself into a Machine Mutant and was in the making of a Machine Mutant army. After his army was sufficient enough to accomplish his first goal, he attacked his homeworld and caused its natives' extinction.
After a while, between Age 760 to Age 770, Myuu had acquired the assistance of an alien who chose to be resurrected into a Machine Mutant. This individual would later become known as General Rilldo.
Rilldo was tasked by Myuu (who was brainwashed by Baby) to go on a hunt for the Black Star Dragon Balls without mentioning it was for the resurrection of the Tuffles. Myuu had also created the Sigma Force to aid Rilldo as his top-men.
Myuu and Dolltaki had plotted the scheme for aiding Baby's power growth by creating the fake Planet Luud's cult under Cardinal Mutchy Mutchy's guise as the priest for the fake deity Luud, whose sole purpose was to fuel Baby with the energies he had gathered within him (the believers were turned into dolls by Mutchy's whip and were fed to Luud's core).
After the defeats of all of the aforementioned villains, Myuu had witnessed Baby's revival on Myuu's Planet and admitted that all he ever wanted to do was not converting the universe into Machine Mutants, but to have them subdued through Tuffleization to Baby, who ultimately kills Myuu for his failures against the Dragon Team and sets out on a genocidal campaign against the Saiyans.