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What is Encounters with the Third Doctor for The Master in Doctor Who?
The Master, played by Roger Delgado, makes his first appearance in Terror of the Autons (1971), where he allies with the Nestene Consciousness to help them invade Earth.
Who encounters the Third Doctor in Terror of the Autons in Doctor Who?
The Master

Question: Who is The Master?
Self-contained rewrite: Who is The Master in Doctor Who?