The Master

The arch-nemesis of the Doctor in the world's longest-running sci-fi show.

The Master appeared in early seasons of Doctor Who, each time with a devious and explosive plot to take over the entire galaxy, enslave its people, cause further explosions, and begin the cinematic trend of depicting evil via moustaches. Roger Delgado is the Master principally credited for this hitherto-unknown use of facial hair as a means of divining moral alignment.

In the course of his many run-ins with the Doctor in Classic Who, the Master carelessly managed to use up all 13 of his lives. Not content to let sleeping maniacs lie, the Time Lords resurrected him for unspecified reasons pertaining to the Time War. By the year one hundred trillion he has ensconced himself in the form of Derek Jacobi and also on the planet Malcassairo, where he occupies himself building engines out of fairy liquid bottles and sticky-backed plastic, aided by his obligatory beautiful assistant.

Plot ensues, and the Master takes on the face of John Simm, who appears to be having far too much fun with the role, and thus not only makes a cracking evil scheming megalomaniac who actually succeeds in taking over the Earth and enslaving its population but also manages to find time to have phonesex with the Tenth Doctor. In his free time he likes to chain up immortals in his big shiny space ship and perform unknowable and unspeakable deeds upon them. He plays the drums.

It is not known if he is the star of Master Who in the mirror multiverse or if the Doctor is called the Master there.