In the Warrior's universe, an incarnation of the Master that the Warrior was unfamiliar with appeared at his trial. The Master helped the Warrior seal the alternate timeline created by the Unified Skaroan Alliance in the Carrisent Particum. (AUDIO: Aftershocks)
Biography
The Master, a former enemy of "the Doctor that Was", fought in numerous battles during the Time War alongside the Warrior. He also stated that he was the Warrior's oldest friend.
However, this timeline was drastically altered after the discovery of the Time Ring on Skaro, during the aftermath of the destruction of the Daleks by the Fourth Doctor. The Unified Skaroan Alliance then used this Time Ring to conquer Gallifrey, the Celestial Intervention Agency and time itself. After winning the Time War, the Alliance placed the Warrior on trial for the genocide of the Daleks. There, the Master was called to give evidence in the Warrior's defence. Unbeknowst to Narvin and the Alliance, the Master was there to help the Warrior seal this timeline within the Carrisent Particum, allowing it to never occur.
From this Particum, the Master was able to speak to the Warrior while he slept, moments after his regeneration. In these dreams, the Warrior would see flashes of this alternate timeline, and would hold conversations with the Master, where the Master would convince him to keep the Particum on his person. (AUDIO: Aftershocks)
Undated events
At some point, the Master died and was resurrected. (AUDIO:The Key to Key to Time)
Legacy
When the White Guardian said that the Warrior’s companion would be their greatest enemy, the Warrior asked if it was the Master “resurrected, again”. (AUDIO:The Key to Key to Time)
Physical appearance
The Master appeared to be an elderly man with thin, grey hair. He was wearing what seemed to be a robe. (AUDIO: Aftershocks, AUDIO: Who Am I?, AUDIO: Time Killers). Although after the train crash he was described as a man with a burnt face, wearing the already mentioned robe (AUDIO Time Killers).
Behind the scenes
As he is played by Geoffrey Beevers, he is meant to be the Warrior's universe version of the Decayed Master. As opposed to his N-Space counterpart, who was burnt by his future self into the Decayed form, (AUDIO: The Two Masters) here he survived a train crash, which heavily burnt his body (AUDIO: Time Killers)