By the Silver Wind - The Summer King Chronicles, #4

The fourth and final volume of the Summer King Chronicles, for ages 11 and up! Shard is a gryfon with a great destiny, and desperate to stop a war. He is hampered on his path to peace by would-be allies, old enmities and grudges between clans of creatures, and the ever-looming threat of the fear mongering wyrms. Everyone believes that Shard is the legendary Summer King, that he alone can make the wyrms see reason and stop their violent marauding before more lives are sacrificed.
But when he uses newfound powers to try communicating with their leader, he only ends up making things worse. When the wyrms make a surprising move by attacking where Shard least expects it, he knows he must be willing to sacrifice anything-and everything-to stop them once and for all.