Torn-out page: Leshen decoction is an alchemy formula in The Witcher 3: Wild Hunt that is needed to craft leshen decoction.
It's a possible spawn at a random diagram location or purchased from the following merchants:
- Herbalist in Hierarch Square
- Yolar at Gedyneith
- Herbalist in Heddel
- All herbalists in Toussaint except Pinastri
It can also be obtained by reading The Heart of the Wilds, but the book never appears during gameplay.