Detoxifying Decoction

Found sitting on a crate in an empty room.

Found in the nearby chest up the cliff when crossing the river.

Inside the chest on the edge of a sloping path that leads out of the large sunlit room.

Break through the wall on the right, then jump over a pit and two collapsible floors. You’ll find the decoction in a chest near another pit.

Inside the chest at the end of the corridor.