Sometime in the 1800s, the third Gorgon possessed an Abbess, who was host until 2007. Several generations of nuns protected this Gorgon. The Gorgon's talisman, which Bea Nelson-Stanley had, was hidden in a box that the Gorgon tried and eventually did find in 2007. At this time she needed a new host, choosing Sarah Jane Smith. Before the Gorgon could do this, with the talisman it could open the gateway to Gorgos so the Gorgons could invade.
Attempting to engulf Sarah Jane, Maria Jackson used a mirror — with the Gorgon's power reflected back on itself it turned to stone. Maria took the talisman out of its place so the Gorgon's could not invade. (TV: Eye of the Gorgon)