Torn-out page: Grave hag decoction is an alchemy formula in The Witcher 3: Wild Hunt that is needed to craft grave hag decoction.
It's a possible spawn at a random diagram location or purchased from the following merchants:
- All herbalists at liberated abandoned sites in White Orchard and Velen
- Herbalist outside the Cunny of the Goose inn
- Jonna in Rannvaig
- Yolar at Gedyneith
- Herbalist in Barrengarth
- All herbalists in Toussaint
It can also be obtained by reading Of Water and Fog, but the book doesn't appear during gameplay.