Medusa (species)

The Medusa was a predator alien species. The Fourth Doctor described them as vile. A Medusa was able to quantum-lock a person, making them petrified.

People who had been petrified were, however, still alive, frozen in time, preserved, so the Medusa could feed on their life energy for years, centuries, even. When the Medusa was done feeding, the petrified person turned to dust. The Medusa were trapped on Earth. (COMIC: Gaze of the Medusa)