Go north. Talk to the girl, using all conversation choices. Go west. Search the dead soldiers body and get the scroll. Go north. Talk to him, using all conversation choices. Search his shelves and get the weird potion. Go south as far as possible, then east, and then north until you hit a barrier. Go west and search the slayer corpses until you get a claw. Go east twice, talk to the man, and say "I have the goods." Go past where the barrier used to be and defeat HIM!