First you have to go Lavandor!
Then you talk to this girl in a house and she requests quite a few items from you. You need to be lvl 22 and give her all the items, then you get Venom Stone.
15:52 Colin: Yes, I need help, I'll need 5 bat wings, 5 nail, 3 tooths, 3 mushrooms and 3 fur. At level 22 you can get better prizes. Are you sure you want to finish it now?