Bottle of Acromantula Venom
Brilliant Hagrid's Hut Exterior
Potions Storeroom, Hogwarts Castle
Acromantula venom is incredibly difficult to acquire. Harvesting venom from a live Acromantula is extremely dangerous due to their aggression, making posthumous extraction the most reliable method. But even that can be tricky, as their venom dries up quickly and Acromantulas tend to cannibalise their dead. These factors cement Acromantula venom as one of the most valuable potion ingredients in the world.