Doctor Who: 10 Worst Things The Master Has Ever Done
4. Helping To Create The Mondasian Cybermen
Yes, yet another Cybermen plot - clearly, the Master absolutely loves them.
There's probably something about their cold and emotionless personalities that he just clicks with, and given their mutually murderous ways, it's no surprise that they've made formidable bedfellows on more than one occasion.
Prior to Series 12, the last time we saw the Master with the Cybermen was in the Series 10 finale, which depicted an origin story for the Mondasian Cybermen. Here, the Master - disguised as a scruffy-looking man called Razor - worked with the residents of a colony ship to enact Operation Exodus, which involved converting countless people into prototype Cybermen.
In World Enough And Time, we learn that these particular Cybermen are in constant pain, and while it's never made explicitly clear how much of a hand the Master had in their creation, he definitely helped the process along.
Oh, and as if that wasn't bad enough, the Master also ensured that the Doctor's companion, Bill, was converted too. He just doesn't know when to stop, does he?