Decayed Master

The Master encountered the Warp Core, which reduced the Master's form back to that of his previous, corpse-like self.

Biography
The Master learned of a device known as the Warp Core, a sentient powerhouse of mental energy designed as a weapon to safeguard the planet Duchamp 331. The Master tracked the Warp Core to Earth, intending to use it to power his TARDIS. Unprepared for its power and underestimating its outside awareness, he was attacked by the Warp Core, having the body he stole from Tremas stripped from him, reducing him to his previous, decaying form. The Master then followed the Warp Core as it arrived on Duchamp 331. (BFA: Dust Breeding)

After the Doctor made a deal with Death, the Master was allowed 10 years in a new life as a good man, then he would be killed. The Master was found wandering the streets of Perfugium with amnesia where he was taken in by Wilston-Croft, and inherited the house when Wilston-Croft died. 10 years later the Doctor and Death came back for the Master. Death made a deal with the Master; the Master would be allowed to live if he became Death's servant, to which the Master accepted. (BFA: Master)

Appearance
After being attacked by the Warp Core, the Master wore masks and gloves to hide his disfigurement. (BFA: Dust Breeding)

Habits and Quirks
As John Smith, the Master's favourite desert was marinated figs with a raspberry coulis, he grew tomatoes, made his own wine, enjoyed theatre, books, and the company of friends. The Master was not fond of dogs or people with shifty eyes. (BFA: Master)