Boss
How to beat Medusa
Patterns
Medusa and The Prophetess are one fight, in the Ossuary of the Innocents. Listed health is 1,500 and experience is 500. She claws, drops snake-hair onto the platform, and petrifies you if you meet her gaze. Turning your back avoids the gaze. The tail is the sweep.
Around 70 percent she rages and the falling rocks are cover. Around 50 and 25 percent the petrify covers the arena. The Lance plus Holy Cross is the loadout the cemetery chapter recommends. Melique Berger voices her.
The reward, stated once
You get Petrifying Gaze and the third guardian key. Who she is in the story, and why the card is called The Prophetess, is on the companion page. This page stays on the hitboxes.
What I ran into
I faced the gaze on purpose to see the animation and ate a full petrify. Turning away is the whole mechanic, and it is the first sentence I would put on a card if I were writing one for the pause screen.
Questions
Where is Medusa?
Ossuary of the Innocents, in Holy Innocents' Cemetery.
Is there a separate Prophetess boss?
No. Same health, same room, same key. The other page explains the name.