The creepiest and most diabolical Master of them all, his shocking return in the Fourth Doctor's story The Deadly Assassin still remains one of the most dramatic moments in the show's 51-year history. At the end of his life, a dying Master returns to play a deadly game with the Doctor, an act that frames the hero for the assassination of the President of Gallifrey and almost destroys the planet itself as the Master attempts to regain a new regeneration cycle by using the Eye of Harmony. This Master was shockingly different to his predecessor - no longer the charming, Moriaty figure audiences saw in Roger Delgado but a deformed, skeletal figure, fueled by revenge as he acts within the shadows. He returned in the Keeper of Traken, played by Beever instead of Pratt and was no less terrible. This time he tried to use the planet's power source to gain new life and when he failed he stole the body of companion-to-be Nyssa's father Tremas. This was the Master at his most horrifying, with Pratt's version in particular the stuff of nightmares.