On Mars, Galvatron Reveiles something to the other Decepticons: while he posed to be The Fallen's servent, he really served someone else, Unicron. Then Galvatron used the matrix to transform mars into Unicron's new body. Upon seeing that, Soundwave, Starscream, Soundblaster, Barricade, & Scorponok retreated to Cybertron. But, Unicron used the cloning machine to create 1,000,002 drones based on Starscream but green. Then Galvatron cloned Starscream 1 more time to make a general to control the drones. The Clone's name was Acid Storm
Later, upon learning what Galvatron did, Springer took Windcharger, Hot Rod, Jazz, Ratchet, Ironhide, Bumblebee, Sideswipe, Arcee, Skids, Mudflap, Jolt, & Blaster to Unicron (Jetfire stayed behind to help the Humans guard N.E.S.T base ). Upon landing on Unicron, most of the Autobots were busy fighting the drones, while that distraction allowed Hot Rod and Blaster to sneek inside Unicron's innards. Upon reaching a ledge that overlooked Unicron's core, the 2 were attacked by Galvatron and Acid Storm. While Acid Storm kept Blaster busy, that left Hot Rod with Galvatron. After some fighting, Hot Rod swiped the Matrix from Galvatron, so Unicron upgraded Galvatron to a Sunstorm-like power level. Hot Rod upgraded into Rodimus Prime, and, after some fighting, Rodimus knocked Galvatron over the edge, and the Autobots, with a captive Acid Storm, retreated on Springer before Galvatron & Unicron exploded, taking the remaining drones with them.
Rodimus used the Matrix to revive Optimus Prime, and turned into Hot Rod again.
Hot Rod/Rodimus Prime
Shockwave (mentioned only)