10 Deadliest Doctor Who Villains
6. The Toclafane
When the Doctor, Martha, and Jack ended up at the end of time, 100 trillion years in the future, they found the last remnants of humanity desperate to leave their world for Utopia. The Doctor managed to help them, but at the same time, the Master made his presence known, and he managed to steal the TARDIS.
When the Doctor meets back up with his old nemesis in the 21st century, the Master had launched a plot to take over the world via the Toclafane, which was the name given to the Gallifreyan boogeyman. In reality, it was the name the Master gave to a race of beings who did his bidding.
That bidding being the near-destruction of Earth and the slaughtering of humanity. When it was revealed what the Toclafane actually were, it broke the Doctor's heart. They were the last remnants of humanity, though they had been grossly altered since he last saw them.
They left for Utopia, but all they found was more darkness. They lost hope and cannibalized their own bodies to be converted into a cyborg race. They ended up with shared memories and a childlike mentality, but that didn't stop them from massacring people by the millions.