Discover the Destroyer — K.A. Applegate

There is a place that shouldn't exist. But does. And there are creatures that shouldn't exist. But do. Welcome to a land where all of your dreams and nightmares are very real -- and often deadly. Welcome to EVERWORLD.

Senna. The one and only reason David, Christopher, April, and Jalil find themselves in a place that is magical and terrifying and wonderful all at once. Senna is also the reason they can't get back to their own world. It seems she only shows up when she wants to be found. And she always disappears.

At the moment, Senna is the least of their problems. Now they have to make a choice: Outsmart the dragon that killed Galahad--or die. And the odds of David and the others surviving by themselves aren't very good. But they've met some Everworld residents that might be willing to help for a price: Senna.