Mumm-Ra is weak and faces the threat of three new Thundercats, so he sends the Mutants to release his old enemies the Lunataks from their imprisonment in order to bolster the forces of darkness.
Mumm-Ra sends the Mutants to release former enemies of him, the Lunataks, to help them fight against the recently reinforced Thundercats. But our Thundercats won't be completely unprepared, as Snarf thinks he heard Mumm-Ra's voice at the Mutants' headquarters.—David del Real