Across the Dark Water — Jennifer Lynn Alvarez

Twelve-year-old Rahkki is a stable groom for the Riders in the Sandwen army, who must battle deadly spit dragons and hordes of warring giants. The Sandwens believe they have tamed all the wild pegasi in the lush jungles of the Realm and turned them into flying warhorses. But when a herd of wild steeds flies over their village, Rahkki and his clanmates are stunned.

Meanwhile, a small herd of pegasi have journeyed across a treacherous ocean to settle in a new, and free, land. Led by Echofrost and Hazelwind, the Storm Herd steeds are unaware of the Sandwen clan. But when the unthinkable happens, Echofrost and the rest of Storm Herd will have to come to trust the Sandwens, or both may not survive.