Omega's life history is shrouded in mystery. Time Lord records and conversations between Time Lords suggest that he existed in the early stages of Galifrey's history and was an ordinary stellar engineer (someone who studies stars and black holes) who was experimenting on black holes with his scientific partner, the founder of Time Lord society called Rassilon. Omega and Rassilon were experimenting on one black hole not far from Galifrey when Omega discovered that by manipulating the energy stored in the black hole, a means of being able to travel through time could be created and used. However, the black hole was opened during Omega's experiment and sucked him into a strange world composed entirely of anti-matter (anti-matter exists separately from matter and is deadly to anything that is itself not composed of anti-matter). Over time, his physical body was destroyed by the corrosive properties of anti-matter and only his very powerful will remained. Omega constructed a mask and armoured suit to protect himself from the anti-matter, and also his servants - humanoid blobs of anti-matter called Gel Guards. Omega ruled this anti-matter world alone and unable to escape. Meanwhile, Rassilon resumed Omega's experiment and was able to channel some of the black hole's energy into the heart of Galifrey, and contained it within a huge 'container' known as the Eye of Harmony. This 'container' allowed the Time Lords to draw energy off to power their time machines, called TARDISes. TARDIS stands for 'Time and Relative Dimensions in Space,' and they were dimensionally transcendental - or much bigger on the inside than the outside. Traditional TARDISes include at least two control rooms, a laboratory, bathroom, conservatory, equipment rooms and dozens of interlinking corridors. Several versions of the original Mark One TARDIS that the Doctor uses, such as the flashier Mark Two and Mark Three, were built after the Doctor left Galifrey. Once he had created the Eye of Harmony, Rassilon set up a large group of Galifreyans called the Time Lords. Over the centuries, these Time Lords multiplied and created the Time Lord race. Rassilon also created the society in which Time Lords live, a strict and orderly society based around conducting time travel experiments, cataloguing the universe's many races and not interfering with any other species. Rassilon led the Time Lord High Council for centuries until his death. He also created the three great holy artefacts of Galifrey - the Sash, Rod and Great Key of Rassilon. These artefacts, when brought together, could unleash unimaginable amounts of power and be used for purposes both good and bad. Omega's name and his remarkable experiment became part of myth and legend, and remains the basis of Time Lord existence and their ability to travel through time and space.
When a hostile gel-like creature was detected causing havoc and destruction on Earth, UNIT and the Third Doctor were unable to deal with the situation on their own. The Doctor called upon the Time Lords for help, but they were experiencing a large energy drain and were only able to send his two previous incarnations to help him. The First Doctor was caught in a time eddy and was able only to advise his two other selves via the TARDIS scanner screen. More and more of these hostile gel-like creatures - actually Omega's Gel Guards - arrived on Earth and soon UNIT was completely overpowered. The Third Doctor and his companion Jo Grant were then bourne across a light stream into a strange anti-matter world, where the Doctor had to fight the mythical Minotaur! On the advice of the First Doctor, the Second Doctor, accompanied by UNIT's Sergeant Benton, deactivated the TARDIS' force field and the whole of UNIT HQ was transported to the anti-matter world. The creator and controller of these events was Omega, who planned to swap places with the Doctor so that he may escape from his anti-matter world and take his rightful place as the supreme ruler of the Time Lords. When the Second and Third Doctors confronted him, Omega flew into a rage and threatened to destroy the Universe. The Second Doctor however, tricked him into touching his recorder - the only thing not converted into anti-matter - and there was a huge supernova (stellar explosion) that apparently destroyed Omega and returned everyone else home. The Time Lords, free of their energy drain, released the Third Doctor of his exile and restored his TARDIS' dematerialisation circuits so that he may be able to travel through time and space once more ("The Three Doctors" 1972).
However, Omega was not utterly destroyed by the supernova. His will remained and as his need for more protection (not from the anti-matter but from any physical dangers he might encounter on his eventual emergence into the world of matter) increased, he created a stronger and slightly different version of his armoured suit and mask. A couple of centuries passed and he discovered another black hole near Galifrey called the Arc of Infinity. This black hole was a link between the anti-matter world where he was trapped and Galifrey itself. Omega planned his next attempt at entering the world of matter more carefully than his previous attempt, getting in presumably telepathic communication with a traitorous Time Lord called Councillor Hedin. Manipulating the lust for power and domination that filled Hedin's mind, Omega promised him such power if he would help his lord and master - the founder of time travel - escape from his prison in the world of anti-matter. Hedin, of course, offered Omega all the assistance that he could give and acted as Omega's "hands" in the world of matter which Omega could not physically interact with. The plan that Omega devised was already in effect when the Fifth Doctor arrived on Galifrey in his TARDIS with his companions Tegan Jovanka and Vizlor Turlough (known simply as Turlough). By the time the Doctor had arrived, the Time Lord High Council had already become aware of the re-appearance of Omega and knew that he was plotting his second attempt at revenge, but they did not know quite what he had in mind.