The Master is one of the most prominent enemies of The Doctor and and like any villian he also tries to take over the world. He met his end after the final confrontation with the Doctor by getting shot by a Cyberman and then exterminated.

The Master


While the Doctor was traveling in the Tardis with Rory and Amy he somehow recieved as warning from Rassilon (who tried to kill both The Doctor and The Master) telling him that the Master has escaped the Time War by stealing a Tardis before The Time Lords could stabilize a lock and that he was after the Wheel of Oblivion.

To try stop him The Doctor went to visit an old friend to try find out more about the Wheel of Oblvion and just as he left to make sure The Master didn`t steal it,he (The Master) unbeknownst to The Doctor was watching him the entire time and left while laughing loudley.