In an alternate timeline, the universe was consumed and left dead by the Master's ultimate form which existed as pure hunger. This timeline was negated when Missy was consumed by her future self, resulting in a paradox.
History[]
The Saxon Master, having been mortally wounded by his next incarnation, Missy, (TV: The Doctor Falls) sought to survive his death and avert becoming her. To that end, he travelled to the human colony on Kiameth, taking it over and using the energy of the planet to thrive and flourish, so that he could heal his own decaying body. Though the colony flourished for a time, he had unleashed a sentient entropy wave, which the War Master later deduced was actually the final form of the Master, that destroyed Kiameth. The wave then spread across the universe, despite the efforts of a parallel Master to combat it by throwing the resources of the Time Lords and the Daleks at it. In the ruins of Kiameth, the Saxon Master used a time scoop to take six of his previous selves out of time (the young Master before leaving Gallifrey, the Decayed Master, the Tremas Master who sent Kamelion in his stead, the Bruce Master, the Reborn Master and the War Master) and brought them to his castle, intending to use the Attornium to take their lives in a desperate bid to survive.
His attempt to time scoop the "UNIT era" Master failed, with Jo Grant being caught instead. The Masters decided to sacrifice her for fun, but were interrupted by Missy. She exposed the Saxon Master's plan and used the time scoop to scatter the different incarnations along the timeline of Kiameth, to see if any of them would find a chance of redemption by either stopping the wave or salvaging something from its aftermath. Missy herself explored the ruins of Kiameth, after loaning her space yacht to the parallel Master, along with Jo. During their explorations they were pursued by the entropy creature and contacted by the Lumiat, who tried to warn them about what the Master had done. The entropy wave caught Jo and Missy reunited with the parallel Master, who conceded defeat and returned to his own universe. Only four of the Masters managed to do as Missy has hoped: the "Decayed", the "Reborn", the "War" and Missy herself. The others, who had turned against Missy, were killed by Kamelion on Missy's orders, though the "Saxon" Master escaped. Despairing about her future, Missy convinced the surviving Masters to use "Saxon's" Attornium to stop the creature by feeding on it, but the "War" Master refused to allow it as the plan would cause a massive energy release capable of destroying any universe. He discreetly poisoned himself and every other incarnation of the Master, having realised the wave was their own future, then turned off the Attornium and left Missy to be devoured by the wave. The resulting paradox erased the events of this timeline, bringing the universe back to normal. (AUDIO: Masterful)