Omega was one of the most significant figures in Gallifreyan history. He appeared in the so-called ROO texts as later scholars on Gallifrey would call them, along with his fellows, Rassilon and the Other. According to a story later told by Omega himself, he originally had the name Peylix but adopted the name Omega in response to his teacher, Luvis who would award him the omega grade in an essay he had written exploring the possibilities of increasing the Gallifreyan power by exploding a star so the resulting energy could reasonably be harnessed for time travel. This, however, was seen by his teacher as madness and pure idiocy; in fact the Omega Grade was the lowest mark possible, and Peylix was left with a humiliating nickname that endured even when he and a friend of his, "Razz", effected this plan and with their technologies combined, forcefully created the race of the Time Lords. By the time of his "death", Omega had married a Gallifreyan known as Patience.
During the Dark Times, it was Omega , in collaboration with Rassilon who enabled the people of Gallifrey to achieve time travel. Rassilon and the Other would assist him in this task. Omega may have also have played a part in the creation of the living metal, Validium.
A stellar manipulator, the Hand of Omega had the power to cause stars to go supernova.
With the power unleashed by a supernova they hoped to generate enough power to make it possible to travel through time.
As Gallifrey's galaxy in which Gallifrey resided had, at one time, only one Population III star, they decided to destroy that on. The star, in the Constellation of Ao bore the name Qqaba.
Officially, Omega died when the star exploded. Two inconsistent accounts exist describing this event. One says that Fenris, a mercenary working for the Order of the Black Sun (a time-active enemy of the Time Lords from the future) sabotaged the stasis halo of Omega's Starbeaker so as to expose it, and the Starbreaker's crew, to the fury of the black hole. Rassilon prevented disaster from overtaking the other three Starbreakers, though Omega seemed to have died.
Omega himself, however, described events as having happened differently.
The Doctor, like most Gallifreyans, would grow up to revere and admire Omega as a great hero. The Hand of Omega had, meanwhile, survived and returned to Gallifrey. The Doctor would later obtain it for himself.
Omega, meanwhile, had gotten transported through the black hole into another universe composed of anti-matter. Omega shaped the universe by force of will and access to the black hole's singularity. He could even create life of a simple kind. Radiation destroyed his body, so that the gauntlets, armour and helmet he had designed to protect him from the corrosive effect of the anti-matter now constituted his physical form. In the beginning, he shaped his new world into a paradise, but as the centuries rolled by he grew weary and depressed, feeling abandoned by his fellow Time Lords, and the landscape slowly transformed into a drab, grey desert. The universe that had become his home was unstable, unable to exist without the will of a powerful mind to give it form; he was trapped.
After thousands of years, Omega hit upon a plan of revenge. If he could capture a Time Lord, he could force them to take his place, allowing him to leave and wreak vengeance on Gallifrey. Using the black hole, he drained power from the Time Lords as a means to stop them for interfering. Omega sent an amorphous life form and other, more humanoid amorphous servitors to find the the Doctor currently serving a sentence of exile on Earth, and take him into the black hole. The High Council, lacking the power to send anyone from Gallifrey to assist the Doctor, decided to send the prior incarnation of the Doctor to Earth to help rectify matters, subsequently contacting and sending his first self to advise them. Omega removed both incarnations to his domain, entry into which converted all matter into anti-matter.
When Omega removed his helmet to prepare his departure, he discovered that the anti-matter universe had completely dissolved his physical body, so he could not leave his universe; he existed only because his will insisted that he exist, but his will was all that was left of him. Consumed by rage and despair, Omega swore to destroy all things. The Doctors offered freedom to Omega, in actuality the Doctor's recorder which the Doctor's TARDIS had accidentally shielded from conversion into anti-matter. When Omega touched this object, it caused an explosion.
Though he was once more thought destroyed, Hedin of the High Council made contact with Omega and decided to help him. Omega had gained control of the dimensional gateway known as the Arc of Infinity. Through the Arc, he had gateway between his own universe and the universe of matter, though he still had no physical form. Omega also had a TARDIS and a servant which he had created, the Ergon. In order Omega needed to bond with another Time Lord using his biodata extract.
Hedin transmitted to Omega the biodata extract for the Doctor, by this time in his fifth incarnation. Omega established a base in the Earth city of Amsterdam and navigated the Doctor's TARDIS into the Arc and, doing this, began to link the Doctor's biodata with his own. The Doctor faced execution on Gallifrey to stop Omega's return. This was all part of Omega and Hedin's plan: they rigged the execution so that it would hide the Doctor and Omega in the Matrix, safe from Time Lord detection. Omega shifted the Arc to Gallifrey in order to gain control of the Matrix and used its power to create a physical body for himself.
The Doctor, however tracked him down and sabotaged his equipment in Amsterdam, forcing Omega to step into the physical universe before the transfer could be made stable. His new body, a replica of the Doctor's, began to decay and turn back back into anti-matter. Thwarted and maddened by defeat, Omega willed the acceleration of his conversion to anti-matter in order to destroy the Earth rather than return to the universe of anti-matter, but was destroyed by the Doctor using the Ergon's Matter conversion gun.
Omega, having seemingly survived once again, had finally captured the Doctor in his Sixth form but was once defeated, and the Doctor escaped his grasp.
Omega was very bitter with regards to his fellow Time Lords who he believed sacrificed him in order to attain greatness. As such, he holds eternal enmity towards his race and seeks to avenge himself against them.
One of his greatest traits was his will which allowed him to reshape the antimatter universe in the singularity to create an environment as well as servants that suited him. This made him linked to the antimatter realm as his will alone kept it alive and prevented his escape. This made him compare his fate to that of the Greek God Atlas, carrying the world on his shoulders. He was completely unaware of the fact that his body had corroded away due to the antimatter realm and that both his physical form as well as the world he created was made by his will alone.