The Priestess of Athena herself told me that at the rear of the temple a cavern opens up and the once High Priestess lives still. Her visage was once as fair as Aphrodite herself and as such she was taken and ravaged by Poseidon as is his want.
Athena would suffer no such recurrence and in a fit of punishment turned Medusa’s fair hair into that of writhing snakes and caused her look to be the death of any man that was to behold it. The priestesses of the temple opened the chamber and found a bottomless pit that reaches all the way to Hades. Many ledges come from the walls and Medusa decorates her home with the statues of those that have approached her and succumbed to her gaze.
I swear this is true and I warn you stranger to look no further into it. Medusa is real and death awaits any that would gaze upon this pawn of the Gods.
Pathfinder Encounters: Medusa Cavern CR 7
It is a dark cavern hidden away in one of the many temples of Athena and it hides a horrifying truth. It hides the creature Medusa of course but it also shows us that the Gods and Goddesses are real and callous. It shows that they care for those that worship them less than we care for the animals we herd from paddock to paddock each day.
You might use this encounter to either have the players seek information that Medusa knows or perhaps Medusa has an item or artifact that the players need to further their quest. You could use it as I have tried to show in the paragraph above, so that you can gain some empathy for the Medusa and cause the players to rage against the Gods!
Either way, you can find the statistics for the Medusa here on the Pathfinder PRD and a nice little Wikipedia page if you want to do some more in depth research on the subject here. I personally feel that the story of Medusa is quite tragic and she gets treated atrociously in Greek Mythology so I would likely introduce her as a figure of tragedy that requires justice, but that is just me!
Falling into the cavern is at least a 400 foot fall so treat damage from an oopsy appropriately as detailed here in the rules.
I hope you enjoy the encounter. As always, leave your comments and let me know how it went. Keep rolling!