Tasha Lem

 was the Mother Superious of the Papal Mainframe and a friend of the Doctor. She was on familiar enough terms with the Doctor to compliment him on his current form upon seeing it in the nude, and for the Doctor to later kiss her. She apparently did not age, as she was "against" it. She also possessed the ability to pilot the TARDIS, telling Clara Oswald that "flying the TARDIS was always easy...it was flying the Doctor I never quite mastered."

Shortly before the Siege of Trenzalore, she summoned the Eleventh Doctor and Clara Oswald aboard the Papal Mainframe. After explaining about the signal from the planet surface, she teleported the Doctor and Clara to the planet's surface, ordering them to return to her in "one hour".

When the Doctor later discovered that Gallifrey and the Time Lords were attempting to return through the scar tissue left by the Cracks in Time, Tasha contacted the Doctor via a massive holographic projection of her face and warned him not to summon the Time Lords back, or else the Time War would begin anew. The Doctor refused to abandon Trenzalore's people. In response, Tasha informed the Church that their new faith would be "Silence". She declared that the Doctor must never speak his name and that "silence will fall."

Three hundred years later, the Daleks – having failed to breach Trenzalore's defences on their own – attacked the Papal Mainframe and slaughtered everyone inside, including Tasha. The knowledge of the Doctor was extracted from her corpse and used to restore the Daleks' lost memories of him. The Daleks also apparently revived, tortured, and killed her several times in a failed attempt to learn how to fully breach Trenzalore's defences. Eventually, she was converted into a Dalek puppet. The Daleks used her to draw the Doctor and Clara into a trap onboard the Papal Mainframe, under the guise of wanting to speak with him.

During the feigned conference, she explained to the Doctor how the Kovarian Chapter of the Church of Silence were responsible for the attempts on his life, even mentioning River Song. Upon revealing that she was actually killed in the Dalek attack three days prior, her Dalek conditioning activated and she transformed into a Dalek Puppet, just as three Daleks entered the room. The Doctor threatened to speak his name, bringing back the Time Lords – and with them the Time War itself. In response, Tasha took Clara hostage, and the Daleks threatened to have Clara killed if the Doctor didn't "die in silence".

The Doctor told Tasha to kill Clara, claiming he didn't care. Clara did not see this as a betrayal, however, as she understood the Daleks planned on killing her anyway, and instead remained by the Doctor's side. The Doctor praised Clara's bravery and berated Tasha for her cowardice. These insults restored Tasha's personality and (after slapping the Doctor) she proceeded to destroy the three Daleks with her Dalek-implanted weaponry. She then told the Doctor and Clara to flee, warning them that she couldn't resist the Dalek programming forever. The Doctor – refusing to abandon the people of Christmas – urged her to continue fighting the Dalek conditioning. She took his advice, and after the Doctor and Clara escaped back to Christmas, 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. She ran into battle on Trenzalore to assist her soldiers. (TV: The Time of the Doctor)

Tasha Lem herself died during the Siege. As a sign of respect, she was buried with a TARDIS key. A fleet of morimentum ships were sent to collect a thousand tonnes of ice each. Over the next thirty years, her tomb was carved out in the ice, and after her burial it was defended by a battalion of Sacristans, assassin androids. She was the last Mother Superious.

Sometime after her burial, Sibling Same and Sibling Different stole the TARDIS key from her grave, and took it to London in the year 1895, where they ensured it fell into the hands of the Paternoster Gang. The Siblings hoped they would contact the Doctor. However, Vastra instead handed the key back to the Sacristan android sent back to retrieve the key. (PROSE: A Perfect Christmas)

Behind the scenes

 * In 2017, Steven Moffat said that he had been frustrated with Tasha's main scene because of how flirtatious her interactions with the Doctor seemed. "What I was looking for was, it was like the Doctor meeting his first girlfriend, you know, and she's now the pope and he's now Doctor Who, so all that's out the window. So they have a certain knowledge of each other, but it's from a long time ago, and they're at ease. I think it went a bit too River Song, because everyone loved River so they sort of made her into another River."
 * According to Moffat in DWM 473, Tasha may have at one time been married to Madame Kovarian.
 * According to Orla Brady, Tasha is mostly human but has some alien ancestry as well.
 * Orla Brady appeared in character as Tasha in a video wishing Doctor Who fans a "killer Christmas".
 * Tasha is both a playable character and an enemy in the Doctor Who: Legacy mobile game.