Queen of the Skithra

The  was the queen and leader of the race known as the Skithra.

In the 1900s she attempted to kidnap Nikola Tesla in order for him to make repairs to her ship, but was thwarted by the Thirteenth Doctor. (TV: Nikola Tesla's Night of Terror)

Behind the scenes

 * Before the episode aired, it was widely believed that the Racnoss would return, given the uncanny resemblance between the Empress of that species and the Skithra Queen.