Lady of Neverness

The  was a being which the Twelfth Doctor described as "impossibility on a cosmic scale". Her physical presence could transform those around her into impossible creatures like her.

History
In the early days of the universe, she was banished to a prison that was out of phase with reality. Every 1021 years, the Falmurian Conjunction caused the skein between universes to thin, allowing the Lady to reach out of her prison through mirrors and other reflective surfaces.

As time passed, the Lady became an urban myth. During some of her escapes, she managed to warp entire civilisations.

In 2015, the conjunction occurred and the Lady was able to reach into the San Diego Comic-Con. The Lady appeared in the countless selfies being taken at the con, with each on being taken bringing her closer to escaping. She managed to escape during the Robert Upney Jr. panel, when many people took photos of themselves near Upney. Emerging from a projection screen, she began transforming those in the room into monsters. However, the Twelfth Doctor used his sonic screwdriver to put the convention-goers' selfies on the screens of the panel room, reminding the transformed who they really were and reverting the changes made by the Lady. At this time, the conjunction passed and the Lady was pulled back to her prison. (COMIC: Selfie)