Here Be Monsters! An Adventure Involving Magic, Trolls, and Other Creatures; The Ratbridge Chronicles Volume 1 Chapter 49

Attack on the Cheese Hall

• Herbert leads their makeshift army through Ratbridge toward the Cheese Hall, but when they arrive, Snatcher and his dudes are gone already.
• Marjorie is there still, though, and she explains that they've put Framley in massive iron armor that makes him almost unstoppable.
• Arthur asks if they used the same iron that Herbert's boots were made of, because if so, he has an idea.
• Quickly, Arthur explains about the magnet in Herbert's cell that would immobilize him if he acted up… Maybe they could use the same idea to stop Framley? 
• Marjorie thinks she can adapt the magnet to be powerful enough to draw Framley in his armor back to the Cheese Hall; the boxtrolls help with some of the mechanics, and the pirates work on getting the beam engine ready to go.
• When they get the magnet switched on, it immediately starts attracting every piece of metal in sight. It's a pretty strong magnet.