An ordinary Viking girl killed after a battle with the alien Mire, Ashildr was resurrected by the Doctor using a Mire repair kit which was able to fix her physiology.

Now with a potentially infinite lifespan, she chose aliases such as Lady Sherade, Ash, El Dir, Alys and the Knightmare, having forgotten her original identity over the centuries.

The last remaining immortal in the universe, preserved inside a reality bubble in the ruins of the Cloisters on Gallifrey, she had lost everyone she knew and loved. As she awaited her final meeting with the Doctor, she sat back, watching the stars die.