Ian McDiarmid (born 11 August 1944) is a Scottish actor and director best known for portraying Emperor Palpatine in the Star Wars film series. He has received an Olivier Award for Best Actor and a Tony Award for Best Featured Actor in a Play for his performances. Wikipedia
The Master — known at times by various other aliases — was a renegade Time Lord, a power-hungry "lover of chaos" who served as both a friend and the arch nemesis of the Doctor.