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. She was afterward converted into a Dalek puppet, with her knowledge of the Doctor being used to restore the Daleks' lost memories of him. 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 proceeded to rally the remaining Church and Silent forces on Trenzalore to fight alongside the Doctor.

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)