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 few Multi-Master stories -- featuring five incarnations of the Time Lord competing to attempt to take over the universe.
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 dependance of seeing the Doctor's reactions to his plans before. (PROSE: Legacy of the Daleks, TV: Castrovalva)