Wicked King by Ana Calin

A secret enemy lurks in the shadow, seeking to destroy the King of Flames and his Queen, the daughter of Hades. In order to trap this enemy and finally reach peace for all the realms, Xerxes and Cerys have to play a dangerous game. One that could claim their lives, especially since they have to keep apart from each other so they can lure the shadow enemy in, make him think that he’s won. But what if his plan is even deadlier than they imagined, designed to bring down all of the nine worlds?