Tasha Lem

 was the Mother Superious of the Papal Mainframe, and an old friend of the Doctor. Shortly before the Siege of Trenzalore, she summoned the Eleventh Doctor and Clara Oswald aboard the Papal Mainframe.

During the Siege, she was killed when the Daleks invaded the Papal Mainframe and afterward converted into a Dalek puppet. The Daleks used her to draw the Doctor and Clara into a trap, but the Doctor was able to inspire her to break her conditioning and help them escape. Tasha too escaped to Trenzalore, where she continued to fight the Daleks alongside her forces.

When the Doctor was dying of old age, Tasha piloted the TARDIS to retrieve Clara so that she could be with him. (TV: The Time of the Doctor)