Perseus

According to Greek mythology, Perseus was the hero who killed Medusa. Before that many warriors had tried to kill Medusa, but they all failed and were turned into stone. (TV: Eye of the Gorgon) He had found the three Gorgons sleeping in a cave. He only watched them through the reflection in his mirror-like shield and was able to cut off Medusa's head without turning into stone. He later gave the head to Polydectes as a wedding gift, who was turned into stone as soon as he set eyes on Medusa's head. (PROSE: Eye of the Gorgon)

The Second Doctor knew that Perseus had used the mirror to defeat Medusa. He told Zoe Heriot about this and used this method to defeat Medusa in the Land of Fiction. (TV: The Mind Robber)

Helen Ayre had studied Greek mythology in her first year of college and had written an essay on the symbolism of the story of Perseus and Andromeda. She wondered if the story hadn't been symbolic at all when she found James Preedy's petrified body. (PROSE: The Suns of Caresh)