Tyrant was created by Galactus eons ago, yet their conflicting styles tore them apart and Tyrant grew jealous of his creator. Galactus is a minimalist, doing his best to survive, knowing that if he feasts on the universe, he'll soon starve to death. Tyrant, on the other hand, simply lived for bloody war after bloody war, to fuel any conquest.
Galactus soon learned of Tyrant's wars, and found them a gross violation of the powers that Galactus had trusted to Tyrant. This caused a battle of epic proportions that destroyed galaxies, and the master, Galactus, won. Tyrant was both exiled, and deprived of his powers of being a Heralds of Galactus. He was still an enormously powerful being and spent eons gaining more power.
He was then chased to the edges of the known universe by the Spinsterhood, who had trained themselves just to battle Tyrant.
Tyrant waited eons for his return and gathered vast amounts of energy to repower himself. Upon his return, he awoke the Spinsterhood from their suspended animation. Unfortunately, too much time had passed and only one survived, Ganymede. She enlisted the Silver Surfer's assistance in battling Tyrant.
Tyrant kidnapped a variety of different space-faring heroes and villains in order to use their combined powers to enhance himself and power his fortress and his robotic army. These kidnapped beings included Silver Surfer, Terrax, Morg, Beta Ray Bill, Gladiator, Jack Of Hearts, and Ganymede. Jack of Hearts, the last of the beings to have been captured, managed to destroy his containment unit before he could be placed into it, rendering him unconscious for the remainder of the following battle but allowing the others to go free. Tyrant defeated all of them, appearing to "toy" with them in the process.
At the conflicts conclusion, Galactus himself arrived, looking for Morg, his current herald. Galactus' arrival disrupted the battle so Tyrant made the decision to offer all the others' freedom to Galactus in exchange for Morg. Galactus reluctantly accepted Tyrant's offer. Tyrant tried to break Morg's will while he was his captive and siphoned much of his cosmic energy into containment devices. Morg was able to resist Tyrant and only wished to serve Galactus, who he believed was the most powerful. This infuriated Tyrant.
The megalomaniac Thanos, needing to prove and challenge himself, teamed up with the likes of Terrax, Ganymede, Jack of Hearts and Captain Marvel. Tyrant implanted Morg with a control device and used him as a defense when his robotic drones were easily destroyed by the intruders. After Morg was released from his control, Tyrant was forced to join the battle himself. After the battle started, Thanos drifted away through Tyrant's fortress, and learned of Tyrant's past, of being Galactus's herald. The remaining intruders were easily dispatched by Tyrant.
Allies defeated, Thanos approached Tyrant, and challenged him to a duel. Using one of Tyrant's containment units, Thanos was able to sustain the battle, yet soon teleported away, having obtained the power orb he sought and proving he can stand against Tyrant. Thanos believed himself to be the victor, but the containment unit he took was but a small version of Tyrant's true power supply.
In anger, Tyrant punished the enslaved race he had appointed as protectors of his fortress. He tore out their hearts and threw their bodies into space. Tyrant then linked himself into his ship and put himself in a state of mecha-catalepsy.
Tyrant was the victim of another theft of his containment globes. The theft was orchestrated by Jakar who intended to use the globe to gain information on how to defeat his enemy the Stranger. Jakar reincarnated Persephone, a member of the Spinsterhood, and reunited her with Ganymede. The Jack of Hearts was used as a distraction while the Spinsters stole a globe from him. The Spinsters wished to face Tyrant as promised, but Jakar teleported them away before they could confront him.
Since Tyrant grew weaker every time Galactus fed, the time eventually came for one of them to die, which may have been Galactus' plan all along. He sent his Toady-Drone to Galactus to arrange a peaceful meeting, but Galactus knew Tyrant would plan to kill him. Morg did not want his master to die so he formulated a secret plan of his own.
When Tyrant arrived to Galactus' ship, the battle began. Galactus tried to make Tyrant a part of his ship, but Tyrant was able to use his power over technology to control the ship and siphon all the biospheric energies from Galactus, leaving him extremely weakened. Soon, Morg entered with the Ultimate Nullifier.
In an attempt to save his own master, the Toady-Drone tried to contain the energies of the Nullifier and bond itself to Morg. It was unsuccessful in controlling Morg, who became controlled by the power of the Nullifier. He used the power to destroy Tyrant's legs. Tyrant pleaded for his life and seemed scared for the first time ever. Eventually, the Toady-Drone could no longer control the Nullifier and it destroyed the ship, presumably killing Tyrant and everyone inside.
Tyrant possessed nearly unlimited cosmic power, he was second only to Galactus. He was able to battle, and defeat, a group of super-powered beings which included:
Silver Surfer, Morg, Terrax, Beta Ray Bill, Gladiator Kallark, Ganymede and Jack of Hearts. His power was so great that he even made a amped-up Thanos (absorbed a large powers sphere prior to the fight) teleport away due to avoiding defeat, or even death.
In Tyrant's original form he was as huge as Galactus and equal in power, but after his loss and depowerment at the hands of his creator Galactus eons ago he was reduced to a lesser modern state. When Tyrant was seen last he drew on the energy of planetary biospheres; every planet that Galactus consumed would leave Tyrant weaker.
Tyrant also has total psionic control over all technology, allowing him to bend any machinery he came into contact with to his own will.
Tyrant commanded a seemingly limitless number of robotic drones who were powerful enough to incapacitate the likes of the Gladiator and Morg. Also, his fortress has equipment with the ability to drain and store the life force of living beings to power his robots and his fortress.