The Barber-Surgeon

The Barber-Surgeon was a Renegade Time Lord who embarked on his own campaign against the Time Lords and Daleks during the Last Great Time War. (AUDIO: The Mission)

Origins
Neither the Time Lords or the Daleks knew the true identity of the Barber-Surgeon. (AUDIO: The Mission)

The Barber-Surgeon himself claimed not to remember much of his life, saying he had a lot of "missing episodes", but he was sure he was always a surgeon and had not been a Doctor. He did recall strangling a companion on the floor of his TARDIS at one point, and also claimed his naming of a pet Dalek as "D4" was based on nostalgia. (AUDIO: The Horror)

The Time War
According to the Daleks, during the Time War the Barber-Surgeon had originally been equipped by the Time Lords to develop weapons. (AUDIO: The Abyss)

From a factory in its own dimension, the Barber-Surgeon created new creatures, regarded as abominations by both warring factions, from the lifeforms that dwelled in the Time Vortex, which he used in a campaign against both the Daleks and the Time Lords. (AUDIO: The Horror) The Time Lords first came to suspect his faction's existence at the recursive inversions at Lakertya, where the Daleks suffered greater casualties despite the Time Lords losing the conflict. At the quantum siege of Zanak, the Barber-Surgeon officially made himself known. The Barber-Surgeon was present when his forces attacked the Daleks at Kembel, terrifying a Dalek survivor who regarded him as "death".

Eventually his attacks endangered the time locks of both Gallifrey and Skaro. (AUDIO: The Mission) The War Council dispatched and two handlers to assassinate him, (AUDIO: The Abyss) however the Barber-Surgeon killed him and took the handlers to his dimension, giving them new personas as "the Constable" and "the Companion". At one point he captured a Dalek, who he named "D4" and kept as a pet. The Barber-Surgeon also encountered a version of the Doctor who remembered a different past to that recalled by the War Doctor, specifically surrounding the circumstances of his first meeting with Barbara Wright and Ian Chesterton in 1963. (AUDIO: The Horror)

The Barber-Surgeon began work on an ultimate weapon; a temporal obliterator which he could use to erase the Time Lords and Daleks which he named the Unforgiving Minute. However he discovered he was dying and would be unable to complete it. In his last days he sought to lure the War Doctor to his dimension, (AUDIO: The Horror) leaving him clues in form of vague transmissions to both sides and the arrangement of the Master's corpse. (AUDIO: The Abyss) He used the Companion and Constable to test the Doctor when he reached his dimension, which confirmed his belief that the War Doctor was still the Doctor at heart and would do the right thing to finally end the war. He gave the Doctor a time ring to escape his dimension and then activated the prototype Unforgiving Minute which erased him and his factory, along with invading Daleks who'd followed the Doctor, from history. As such, the Doctor also reasoned that everyone killed by the Barber-Surgeon was restored to life. (AUDIO: The Horror)