With the show's 2005 revival, executive producer Russell T Davies stated his intention to reintroduce classic icons of Doctor Who one step at a time: the Autons with the Nestene Consciousness and Daleks in series 1, Cybermen in series 2, the Macra and the Master in series 3, the Sontarans and Davros in series 4, and the Time Lords (Rassilon) in the 2009–10 Specials.
In what series was the Master reintroduced?
3