[The] Master /ˈmɑːstə/: Renegade Time Lord. Originally called Koschei. Known as the Doctor’s arch-nemesis. He took several names in order to reach positions of power, one of them being Harold Saxon, Prime Minister of Great Britain. His diabolical madness was the result of a never-ending drumming sound that had been retroactively implanted inside his head by some of the Time Lords on the last day of the Last Great Time War in an attempt to escape the event. The Master used all of his regenerations but obtained a new cycle from the Time Lords, being last seen in his seventeenth incarnation.