Getting a Head

The trick is getting a Preserved head rather than a plain rotting one: you must lop the medusa's head off while she still has a healthy chunk of HP - roughly her first or second health bar - so soften her up but don't nearly kill her before you decapitate (see 594046910 for the how). The head then decays quickly, so the instant you have it, fast-travel straight to a town and dump it in your storage to freeze the timer. Keep it fresh - you'll want it for 506406635.