The Master is a being shrouded in mystery and betrayal. In his younger days he was known as Aelomir, Dark Lord of the Sorcerers. He is the son of Aeylmaar, and the father to Phalomir. Like his father and grandfather before him, he was knowledgeable in the All, and used it to manipulate time. In his wanton dabbling he foresaw the coming of the Vong and became obsessed with finding ways to prepare for their invasion. Aelomir went mad with this obsession, and eventually concluded the only way to truly save the Sith was to turn to the denizens of the Darker Realms for assistance. He struck a bargain with the Lords of the Darker Realms, agreeing to trade his son Phalomir for great powers that would save the Sith.But during the trade, Phalomir came into his own powers and managed to escape. Aelomir was in danger of being trapped in the Darker Realms, and tried to use his All powers to escape. His initial instinct turned to his obsession: time. He was sent backwards 100 years and still was trapped in the Darker Realms.
But here he made new acquaintances, such as Lord Roan, who introduced Aelomir to his own grandfather, Aelvedaar. Dark bargains were struck which would benefit all and appease the Lords of the Darker Realms, who were upset when they accidentally learned of the bargain made in the future for Phalomir.
Taking the name “The Master”, Aelomir concocted an elaborate scheme to trap Phalomir. He convinced an eager spirit, Thoran, to be his messenger, and send his spirit back through time to meet with Phalomir as he attempted his own plan to save the Sith from the Vong (see that story elsewhere). When that plan failed due to Phalomir regaining his memories through his love for Graysith, the Master turned to a more straightforward approach. He used the All and the power of the Darker Realms to project Thoran’s spirit back into the physical world, where he could swap places with the soul of other beings.
The Master retained a tight link with Thoran until the Eye of R’lous cut the connection and freed Thoran. Now the Master is regrouping, but is still focused in his madness, trying to trade his son (complete and intact) for victory over the Vong.