Classic Halloween image. The lightning lit castle on the hill. Looming over the town below. The perfect hook for a halloween or horror game experience. Assuming your players will take the obvious bait in the even more obvious trap that you want them to walk into. Of course they could do the completely logical thing and burn the castle to the ground. Or siege the castle. Or any number of intelligent courses of action that don't involve walking into the trap. Darn those players for thinking when you don't want them to and not thinking when you do want them to.