The Five Masters was a backup comic printed in the back of Doctor Who: The Twelfth Doctor issue 12. It continued the story printed in the previous three back up stories of the Doctor and Clara being forced to perform in a music competition in order to save their lives. Like The Abominable Showmen before it, this story is notable as one of the first multi-Master stories, featuring five incarnations of the Time Lord competing to attempt to take over the universe.
Remarking that he didn't know when he was well off (something he's always wanted the chance to say), the Doctor is approached by Missy who asks how he hopes to stop them. Far from being intimidated, the Doctor declares he will be doing nothing to stop them, in fact he can barely bring himself to care about this plan, even as Missy begs him to ask. When she brings out her device, the Doctor, with an explosive sigh, guesses that the plan involves hypnotism before leaving her to it, much to Clara's confusion.
As Missy begins her performance, she and her previous selves begin fighting over the device, each wanting to be the one that brings about galactic conquest. As the Doctor explains to Clara that so many egos in one room could only lead to in-fighting, the Masters are teleported away and it is their turn on stage.
The Doctor says, "I didn't know when I was well off", upon seeing the many Masters, noting that it is something that he has always heard others say and has always wanted to say himself. (TV: The Three Doctors, The Day of the Doctor)
When the Doctor shows little care in the plan concocted by Missy and the Masters, Missy comes close to begging the Doctor to ask what their scheme is. The Master has noted his dependence on seeing the Doctor's reactions to his plans before. (TV: Castrovalva; PROSE: Legacy of the Daleks)
The Doctor and Clara recall their previous discussions of the creative differences which had befallen a band of the first four Doctors as the five Masters fight. (COMIC: Day of the Tune)
According to one account, the Master had the appearance of Roger Delgado while on Gallifrey. According to another, he had Anthony Ainley's likeness. According to another one, the one with James Dreyfus's appearance was the incarnation who ran away from Gallifrey.
While fighting to extend his life at the end of his regeneration cycle, many bodies were possessed by the Beevers incarnation, but all kept somehow reverting to his real being until he finally regenerated into the MacQueen one. Hence, these sections cannot be strictly chronological