Galvatron explained to Shockwave and the remains of Megatrons army, that apparently he, Cyclonus, Scourge, and Trypticon were from an alternate dimension where things are vastly different. Galvatron, Cyclonus, Scourge, and the Sweeps were reformatted by a gigantic planet transformer named Unicron.
He told them that he used to be Megatron and that Starscream threw him and other injured Decepticons into space after a major battle at Autobot City. He then returned and vaporized Starscream. He then began the Matrix Quest for Unicron. The Matrix was obtained and brought to Unicron.
The Autobots tracked it down and the Autobot leader named Rodimus Prime temporarily beat him, and he drifted through space to a plasma planet named Thrull.
Since the Decepticons lost the great war, they were banished to a burned out planet named Charr. They were suffering badly from Energon depravation. Cyclonus and the Sweeps decided to find Galvatron. They tracked him to Thrull and brought him back to Charr.
Motormaster gave his last bit of Energon to aid in the search for Galvatron and subsequently went offline. Galvatron never forgot this loyalty and that was why he utilized this chance to help him.
Later when the key to the Plasma Energy Chamber was sought, the search led to a planet called Nebulos and the Headmasters and Targetmasters were created.
Galvatrons army eventually returned to Autobot City on Earth. They captured Metroplex and reprogammed it into Metrotitan. All but a few stranded Autobots on Earth were slaughtered, including Rodimus Prime. The Decepticons held the entire Western hemisphere, of Earth. Galvatron enslaved the surviving Autobots, and mockingly, called them the Anti-Cybertrons. During the remaining Autobots revolt, Galvatron and the others were ejected from their time by a massive nuclear attack, which interacted with The Heart of Cybertron, in Nemesis, that opened a transdimensional portal.
After the tale was finished, the Decepticons accepted Galvatrons leadership. Plans for departure to Charr were made. Since the Autobots were stranded on Earth, they would not be able to stop the Decepticons.
Trypticon was sent to demolish the Ark, just to be sure.....
After that was done, the Decepticons abandoned the Earth, and headed for Charr.
