In “Remembrance of the Daleks”, the Doctor muses “You can always tell a man by the quality of his enemies”. To me, the Master is the most definitive enemy of the Doctor.” He is everything the Doctor isn’t. He manipulates time and space for his own goals, while the Doctor would rather maintain the flow of time correctly, because he knows how dangerous changing events is. The Master manipulates people, either compelling them to do his bidding unwillingly, while the Doctor would rather respect the freedom of others.
As with Doctor, several people have played the Master since his appearance in “Terror of the Autons”. This editorial is my personal ranking of the Masters.
Summary: The Doctor and Ace return to Perivale, and Ace discovers no one remembers her and all of her friends are gone. A mysterious race of aliens that are half-cheetah, half human are attacking people. The Doctor and Ace discover that they are in league with the Master. But the Master has changed. He has become like these creatures, so savage that he is no longer himself. And the same thing happens to everyone they come in contact with.