Potion of ClearanceYou can get a Potion of Clearance from Keira Metz, who is also the first person who will be able to sell it to you. When you finish the Magic Lamp quest and start the next one, An Invitation From Keira Metz, travel Keira’s hut north-east of Midcopse and ask to see her wares. The potion will be among them and will set you back 1000 Crowns. If you plan on redistributing your ability points, this is money well spent.
You will later be able to purchase the potion in Novigrad, in the plaza north-east of Hierarch Square. There is a building on the plaza’s west side; its proprietor will sell you the Potion of Clearance for 1000 Crowns – the same price as Keira’s. You won’t be able to buy the potion immediately, however, since you will first need to talk with him about some artifacts.