The Muta-Do is the leader of the Mutai.
The Muta-Do decides on who may enter into the Mutai, a "no holds barred" fighting circuit. According to Mr. Garibaldi by 2258, the Muta-Do (over ninety years old at the time) had personally fought in over 1,000 matches.
He initially denied Walker Smith access, as the Mutai had been off limits to humans. Following some training by Caliban and a direct challenge to the champion of the Mutai, Smith was able to compete in the Mutai.