Find Serpents’ Lair
After obtaining Arcane Whip, return through Holy Innocents’ Cemetery and descend into Roman Baths. Use the grapple route, operate the lever on the way and refill at the mirror before Serpents’ Lair.
Avoid the gaze
When Medusa begins her gaze, turn Rose away from her. Wait for the effect to pass before facing her and attacking again.
The arena has water and floating platforms. Keep an escape route, reposition before committing to a combo and use short attacks during recovery. You cannot directly grapple Medusa with Arcane Whip, so do not rely on grappling behind her as if she were a humanoid target.
Rewards
Absorb The Prophetess to obtain Petrifying Gaze and the Prophetess key, one of the three Catacombs keys. Petrifying Gaze becomes Rose’s spell; it does not grant automatic immunity to petrification.