Dracengard: Book 1 by Christopher Vale

It has been over a thousand years since the last Realm War, when the angelic seraph and their dragon allies banished the demonic shedom back to the Realm of Darkness. Now a new evil threatens the Middle Realm as a self-proclaimed wizard and a mysterious black knight lead an army of humanoid lizards against the kingdoms of man.

To save her home, Princess Terrwyn will join her twin brother Erec and little sister Taite on a desperate quest to find Dracengard, a mythical place that few believe even exists. They must brave man-eating monsters, demonic knights, and opportunistic pirates as they flee the Wizard’s clutches with a magical stone that legend claims holds the power to destroy the forces of darkness.