Liar's Sanctuary: The Last Book of the Kings series

Brazen treachery tears apart the Second Kingdom by murder within the royal family. In the north, a new kingdom called Sanctuary proclaims a stolen infant as the rightful Keeper sovereign, while in the south, grief-shattered King Colin and his people begin to heal. As the ensuing years bring rumors of war, and a long-foretold Destroyer arises, two Keepers inherit the task of mending their uncle's broken kingdom. Lucien, the obedient firstborn, and Marcus, the impetuous youngest son, leave family and home to live secretly among the rebels, only to find that the poverty spawned by corrupt authorities threatens their mission at every turn. Meanwhile, in Sanctuary's ancient monastery of Maergrethe, a solitary girl grows up in name a queen but treated as a prisoner. Despite her many disadvantages, Sunya believes it is her destiny to overthrow the man who murdered her mother. Will she recognize help when it comes, or will years of bitterness cause a crucial delay, endangering not only the brothers' mission but the lives of everyone in Sanctuary?