Thirty books, some the kind you could pick up in your local library, others that are carefully hidden away from the general public for good reasons.
30 books to be found within a steampunk setting. Manuals, tomes, and blueprints galore!
A cave with weapons sunken into the walls, blades sticking out of the floor and ceiling, and so on. Possibly, any weapon used in it could be torn out of the hand and sink into the stone.