The Poisoned Crown — Amanda Hemingway

Nathan Ward's unique ability to enter his dreams and parallel worlds has followed him into adolescence. With Nathan's growing maturity comes a deeper understanding of his mission; he must stop an insidious and pervasive evil. Queen Nefufar's dark power is growing. In the strange world Nathan visits, land is a distant memory, save for the rumored islands and melting ice caps. The queen's dream of extinguishing the lungbreathers, including man, and ruling over a watery kingdom of cold-blooded creatures is in reach.

Meanwhile, in another dimension, on Earth, there are rumblings of doom. Nathan senses a shift in the atmosphere, and the wizard of the Cosmos broods over the imbalance. There is one chance for salvation: Nathan must capture the third Grail relic, a poisoned iron crown that Nefufar keeps locked beneath the ocean in a chamber of air. But how can a mere boy make his way millions of miles down into the boiling, watery depths and capture the crown from a ferocious seadragon?