1.After getting the „Control your lust“ quest (see Mira's quest 3.) buy Anesthetic from his shop
2.Walk over to the witches cottage. Talk to her. Select option 3 (even if you don't plan to do so)
3.Make sure (lust<80) talk to her again and ask „About my situation“ - Distract her. While she is up looking for her potions walk over to her cauldron and put in the Anesthetic(Alternatively to using the Anesthetic, If you already did Gwen's quest you can wait until she leaves the room and then search the bookshelve)
4.Hide outside the room
5.Search the book shelves until you find a book about potions (You will only find the book if you've learned reading, see Mira. It's on the left side and you have to complete an int-check)
6.Talk to Lucius and give him the book. After that he wants a sample of your sperm (use Masturbate) give it to him and come back the next day
7.From now on you can buy empty vials at his shop and sell bottles of cum to him this will raise your C (the amount you sell him will have effect on other events: Kate serving)
8.You can buy a new leather armor at his shop (near the window)
9.7 days after you completed L7. (If using old saves this might differ) Talk to him again and he will offer you a new potion which will stop your lust building for 5-8 days and also prevent you from causing corruption when cumming in a girls mouth
10.There is a pickaxe on the top right shelf that you can buy to mine copper in the forest (Need strength)
11.You can buy the map on the shelf in the middle to enable fast travel to villages you've been to. (use options > keybinds > bind open map to 'M' or whatever you want it bind to or open the map via items)
From the walkthrough of Chyos.
You are too lazy to read some shit.