Mestizer

Mestizer was a shapeshifter who had a long history with the Doctor.

Mestizer was a time sensitive. Amongst her talents, she was a hypnotist and a mystic, could read minds, and was described as a "powerful creature with many followers." (PROSE: The Tunnel at the End of the Light)

Mestizer encountered the Doctor at the bay in London in 1949. Shortly afterwards, someone shot him in the back and he regenerated into a new incarnation. Mestizer employed gangsters, some of which she had reshaped into monstrous forms, in order to secure the Doctor's TARDIS. She frequently bathed in a liquid which she claimed had restorative qualities. (PROSE: The Cabinet of Light)

In 1950, Mestizer commanded the Subterraneans to kill several individuals across London, setting the Demon King free. Mestizer was killed by the Demon King as it broke free from the London Underground, but after Honoré Lechasseur and Emily Blandish changed history to stop the Demon King, the events leading to Mestizer's death did not occur. (PROSE: The Tunnel at the End of the Light)

Behind the scenes

 * Author Daniel O'Mahony intended Mestizer to be an incarnation of the Master; she preceded the first "official" female Master,, by 11 years.