Six years after the decisive battle against Unicron, a group of rebellious Headmasters led by Weirdwolf join with Galvatron's Decepticons in an attack on Cybertron. The Headmasters, led by Cerebros, return to their home planet to aid in its defense. The situation soon gets worse when it is revealed that Vector Sigma, the super-computer at the planet's heart, is destabilizing, and Optimus Prime again sacrifices his life to save Cybertron. This proves to be only delaying the inevitable, however, as a bomb attack instigated by Scorponok turns Cybertron into a burnt-out, inhospitable husk. Rodimus Prime departs to search for a new planet for the Transformers to live on, leaving Cerebros in command, operating from the planet Athenia. Meanwhile, Scorponok replaces Galvatron- who had vanished in the explosion- as Decepticon leader, constructing a personal Transtector and redubbing himself MegaZarak to battle Cerebros' own giant form, Fortress Maximus.