Alchemy is one of multiple crafting systems that you'll use in Kingdom Come: Deliverance 2. You'll need to use alchemy to complete some quests, but it's generally useful throughout the game due to the potions you're able to craft with it.

To complete Osina’s request, go to the privy next to the combat arena that you visited during the Opus Magnum quest, then interact with the stalls to reveal the demons. Since it just looks like a loo to you, go back to Osina and he sends you off again to investigate a mysterious door on the Maiden side of the tower.

Deliverance 2 players will come up with a Nomad camp in Lower Semine that will have one of the most challenging questlines in the game. Starting with Miri Fajta, Henry will have to deal with family feuds,