Stheno

According to Greek mythology, Stheno was a Gorgon. Her father was the sea god Phorcys and her mother was Ceto. Stheno was the sister of Euryale and Medusa. (TV: Eye of the Gorgon)

Behind the scenes
In the Doctor Who universe, as in the myth, there were three Gorgons on Earth. Eye of the Gorgon does not explain, however, whether Stheno is the Gorgon defeated by Edgar Nelson-Stanley in the 20th century, or the Gorgon defeated by Maria Jackson in the 21st century.