The Decepticons get the key back and return to Cybertron. Galvatron has a giant engine built on Cybertron to move it close to Earth's sun. He uses Cybertron's plasma chamber to attempt to turn the Earth's sun nova and capture the energy. Optimus Prime arrives on Nebulos after a conference with Alpha Trion and the Autobots pursue the Decepticons, except for pacifist Cerebros and Spike who stay behind.
Cerebros is convinced by Spike to help rebuild an old Hive city, defended by drones Gasket and Grommet. As the Autobots are threatened with defeat on Cybertron, the city arrives with Spike and Cerebros. Spike becomes Cerebros's head and Cerebros becomes the head of the transformed city, now Fortress Maximus. Fortress Maximus defeats Scorponok. Spike and the Nebulons use the giant engine to suck the surplus off of the Sun before it novas and uses that energy to bring about a Golden Age on Cybertron. Scorponok and the Decepticons flee off into space. Great Scene: The coming of the Golden Age to Cybertron is a truly c scene.