Gorgon (mythology)

The Gorgon was a hideous creature possessing snakes for hair and the ability to turn whoever looked upon it into stone. Originally from Earth, it came to Zeno and began turning the inhabitants to stone. When the First Doctor, John and Gillian arrived on Zeno, they saw all the statues and realised what had happened to the people. They put on blindfolds and used Gillian's mirror to show the Gorgon its reflection, turning it to stone. (COMIC: The Gaze of the Gorgon)

After her death, Katarina saw a gorgon in the Underworld. (PROSE: Katarina in the Underworld)

Behind the scenes
The Gorgon in this story seems to be of a different species than the Gorgons encountered by Sarah Jane Smith.