Beast Man is the savage right-hand man of Skeletor. He is a character appearing in the Turtles of Grayskull (mini-comics) and Turtles of Grayskull (comics).
Turtles of Grayskull[]
When the villainous Beast Man shows up at Palace of Eternos, he is quickly captured. He says that Skeletor summoned an emerging power to Eternia, which turned out to be a bridge to another universe. This dropped Krang and Shredder in the middle of the Swamp of Gangoon. Skeletor struck up a partnership with Shredder and Krang to utilize mutagen to conquer first Eternia, then Shredder and Krang's world. Beast Man tells them that he witnessed Ram Man, Moss Man, and even He-Man himself captured and subjugated to the mutagen. Claiming that he came to the palace to seek help because he didn't want to be mutated, Beast Man agrees to lead a team to infiltrate Snake Mountain. Belly of the Beast (Man)
Beast Man is among the Evil Warriors, in service to Skeletor, who join the major battle against the Masters of the Universe. Turtles of Grayskull issue 1