Mestizer

Mestizer was an individual who had a long history with the Doctor. She was an exceptional hypnotist (PROSE: The Cabinet of Light) and a time sensitive. (PROSE: The Tunnel at the End of the Light)

She was implied to be a shapeshifter, telling Honoré Lechasseur "you don’t want to see me when I take my skin off." Eric Walken described her as "the dark lady, [...] the spider woman, the evil seductress who tempts man and brings about his destruction." (PROSE: The Cabinet of Light) Amongst her talents, she was 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 such as Abraxas, in order to secure the Doctor's TARDIS. She frequently bathed in a liquid which she claimed had restorative qualities. Aside from speaking English, she also spoke a sing-song language which only the Doctor could understand. (PROSE: The Cabinet of Light) One of Mestizer's hypnotised lackeys, Amber, used the nursery rhyme "Mary had a little lamb" spoken backwards as a summoning incantation. (TV: The Dæmons)

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 the Master; she preceded the first female Master seen on TV,, by 11 years.