Riders of Destir: The Seventh Dragon — A.D. Miller

Condemned and hunted for a murder he did not commit, Prince Eilrach of Pelinor soon realizes that much more hangs in the balance than the ruling of his country. Discovering that his brother, Kerinor, may soon have access to the most powerful weapon in all of Destir, the Diamond of Jazel, Eilrach must search to find the only objects powerful enough to defeat Kerinor and save his world, the gemstones that once belonged to the first Riders of Light, Shadow, Flame, Water, Lightning, and Earth. Along with his black dragon, Shadowstorm, and other Riders he meets along the way, Eilrach encounters death, betrayal, laughter and love in his race to find the six stones before it's too late and Destir is thrown into chaos.