Following Delgado's sudden death in a car crash in 1973, the Master disappeared from the series for several years.
On his next appearance, in The Deadly Assassin (1976), the Master appeared as an emaciated wreck (played by Peter Pratt under heavy make-up). Although Time Lords have the potential to postpone death by completely renewing their bodies, the ability can only be used twelve times. Unlike the Doctor, the Master had in the course of his career used up all twelve of his regenerations, and was nearing the end of his thirteenth, and presumably final, life. He attempted to seize control of an ancient power source (the Eye of Harmony, an artificial black hole maintained on Gallifrey) in an attempt to give himself a new cycle of regenerations. After being defeated by the Doctor, the Master disappeared from the series once more.
In 1981, the Master became a recurring villain again. In The Keeper of Traken, the Master (played by Geoffrey Beevers under different heavy make-up) briefly gained control of another ancient power source, using it to transplant himself into the body of a Trakenite named Tremas, overwriting Tremas' original mind in the process. Now played by Anthony Ainley, the Master appeared on and off for the rest of the series.
The Master also appeared in the 1996 telemovie (see Enemy Within) that starred Paul McGann as the Doctor. In the telemovie, the Master's current body (played - for mere seconds in the final edit - by Gordon Tipple) was thoroughly executed by the Daleks, but he managed to survive by some unexplained means and steal a new one (played by Eric Roberts). The Master once again attempted to access the Eye of Harmony to grant himself a new cycle of regenerations, this time via the Doctor's TARDIS power tap, but was sucked into it and apparently destroyed.
The Master has also featured in spin-offs of the series, most notably David A. McIntee's "Master trilogy" of novels comprising The Dark Path and Final Frontier in the Virgin Publishing lines and The Face of the Enemy for BBC Books, and the Doctor Who audio dramas produced by Big Finish Productions, where Geoffrey Beevers has reprised the role. In 2004, he was voiced by Derek Jacobi in the animated webcast, Scream of the Shalka.
