“ In this dungeon, the monsters will not be hostile unless you take something without permission. If you do take something, the monsters inside will consider it stealing and attack you.”
“ A Deity of some sort has unleashed a plague of bookworms or something like that in the area. Almost all spellbooks are destroyed, along with bardic and historical books.”
“ The PCs accidently start a fire and are caught by the local law enforcement. Since it was accidental, the punishment for the PCs is to fight the fire. Providing they can put it out before it burns down the town, they will not face any further punishment.”