BookBarbarian
Expert Long Rester
The medusa description in the MM is very specific about how to end the petrification: The petrification lasts until the creature is freed by the greater restoration spell or other magic.
In my current campaign, one of the PCs was turned to stone by a Medusa and after the rest of the group killed the Medusa they took some of her blood and found an alchemist to make a potion to restore the stoned PC. Something like that could work.
Let them make medusa blood stone-to-flesh potions.
Edit: Technically "oils".![]()
I'd let potions brewed from medusa remains fall in the "other magic" category specified in the monster text, but not go for the killing it ends the effect option.