In the distant past, the devourer of worlds, Galactus, created an immensely powerful living machine: Tyrant. However, unlike his creator, Tyrant developed a lust for tyranny and conquest that directly conflicted with Galactus' desire to do only what is necessary to survive. Tyrant's conquests aroused opposition in many forms including an order of super-powered female warriors called the Spinsterhood, of which Ganymede was a member.
Eventually, Galactus learned of Tyrant's betrayal and engaged him in a titanic battle that unleashed energies that (according to Thanos) destroyed whole galaxies.
In the end, Galactus barely defeated Tyrant, stripped him of the bulk of his power (thereby reducing him to his current stature and power levels), and banished him to the farthest corners of the universe. The Spinsters mistakenly believed they were responsible for driving Tyrant away, when in fact it was his defeat and depowerment at the hands of Galactus that had done so, as Ganymede later learned.
Tyrant returns eons later with a vast arsenal he built during his exile to resume his conquest. He kidnaps a varied selection of space-faring heroes and villains in order to harness their combined powers for himself. Those kidnapped by Tyrant to this end were Silver Surfer, Terrax, Morg, Beta Ray Bill, Gladiator, Jack of Hearts and Ganymede. Jack of Hearts, the last of the captives to have been captured, managed to destroy the containment unit before he could be put into it, rendering him unconscious for the remainder of the ensuing battle but freeing the others. Tyrant defeated them all, seeming to "toy" with them in the process. At the end of the conflict, Galactus himself arrived, searching for Morg, his current herald. Galactus' arrival disrupted the battle so Tyrant decided to offer all the others' freedom to Galactus in exchange for Morg. Galactus reluctantly accepted. Thanos of Titan, seeking a challenge, allied himself with Terrax, Ganymede, Jack of Hearts and Captain Marvel to learn about Tyrant.
When the group attacked Tyrant's fortress, Thanos abandoned his allies to access Tyrant's computers while they battled Tyrant. Thanos learned of Tyrant's origin and of his defeat at the hands of Galactus. After his former allies were defeated he threatened to steal the orb containing Morg's energy that Tyrant drained from him. He challenged Tyrant to stop him. Thanos, through the aid of the the stolen orb, was able to withstand Tyrant's attacks while the others escaped on Thanos' ship leaving him alone against Tyrant. In the end, after surviving a tremendous assault that destroyed much of Tyrant's fortress, Thanos teleported away. Thanos declared that he had gained what he sought (the said power orb) so further conflict was pointless. He also pointed out to Tyrant that being able to hold his own against him was a success in itself.
Tyrant later revives the herald Morg and implant mental controls in his mind to make him do his bidding. He allowed Morg to return to Galactus as a ruse, but Morg managed to defy Tyrant; seeking out the Ultimate Nullifier, the only weapon in the known universe that even Galactus feared. In a final battle between Galactus and Tyrant, Morg used the Ultimate Nullifier, destroying Galactus' ship and seemingly destroying everyone aboard - including Tyrant.
Galactus later reappeared - it was revealed that he had avoided nullification by escaping into a parallel dimension. Morg (only as a corpse) and Air-Walker later resurfaced during Marvel's Annihilation event. Tyrant for now is assumed dead.