The thematic importance of rules, both magical and mundane, is prominent in Fablehaven. Rules serve to maintain the balance of the preserve, and because of her strict adherence to them, they also serve to keep Kendra safe during the defining battle at the climax of the novel. Further, Mull makes an argument about when and why to follow rules—and when to break them.

Grandpa tells Kendra and Seth about the agreements that Fablehaven is built on just after they drink the milk for the first time. He tells them that “the fundamental premises of the law are mischief for mischief, violence for violence. [The magical creatures] will not initiate trouble unless you break the rules. You have to open the door. If you harass them, you open the door for them to harass you” (79). These rules are what keep Fablehaven functional. The preserve requires humans to function, and the magical creatures that live there need the preserve to be free from the dangers of the outside world.

Kendra’s unwillingness to rebel or risk breaking the rules is what ultimately keeps her safe so that she can save the rest of her family.