[1] Gone

The dragonriders live in peace, even with the famine that's struck their mountains- all turned around by a surprise attack from the human tribe. The village burnt and most of their friends and family dead, one friend group is forced to flee, where they're separated. They lose dear friends and find new ones, who open their eyes to a world unknown...
Or maybe it's the same world, just a lot more to it than they thought.