After months of searching for the secrets of her past, Enna Summerlark has finally found the answers she sought. In doing so, however, she has unwittingly helped to throw the world into complete chaos. With the Praetor of the Council of Tymenthia dead, a centuries-old spell keeping arcana in check across Olhéan is broken, stripping arcanists of their powers, and freeing the demon Nebalsus from Its prison. Enna and Erasmus find themselves stranded on the continent of Shahtyr, trying to find a way home to undo the damage that has been wrought. Half a world away, O'doc and Odonwa struggle to make sense of a world suddenly turned upside-down, with no explanation as to why. With their search for their missing friends at a stalemate, the halflings embark on a search for their aunt Caliope, unaware that the war between Lohvast and Hallowspire is only just beginning, and that a nascent traitor may be in their midst. With Enna and her friends torn apart, and the fate of the entire world hanging precariously in the balance, Collapse of Kingdoms raises the stakes to their highest, offering up the thrilling conclusion to the Four Kingdoms Saga.