The Sound Stones

Vultureman develops a sonic gun to destroy the Thundercats. Since the other Mutants refuse to help, Vultureman decides to go on his own until the Lunataks ""kidnap"" him and force him to help them. Vultureman uses a legendary sound stone to power the device and he and the Lunataks use it against the Thundercats at the Tower of Omens. The Thundercats barely escape and are saved by Lion-O, but they lose the tower to the Lunataks. The Thundercats must design a sound weapon of their own with a sound stone to counter Vultureman's weapon and retake the Tower of Omens.