Doctor Who: The Lost Stories: Alixion (9.2)

Checking into a luxury health spa for a little rest and recreation, the Doctor and Ace find themselves at the mercy of a malign entity that craves the conquest of time and space.

Exploiting their memories and regrets, the queen of the hive, which hides behind the polished walls of the spa, forces them to confront their deepest fears as she steals the Doctor's life force to spread her powers across the universe.