Starforged: Legends of Pangea Book 4

Enoch and Jacob race against time to rescue Enoch's younger brother, Sam, who is being held captive for a sacrificial offering to a river god. Well hidden behind a waterfall, a secret vault contains the skeletal remains of a hero, and the worlds most dreaded warlord. After looting the vault, Enoch learns that he may have opened the door to the long-prophesied return of the evil warlord. He must choose between his heart's desire, to reunite his family, or to save a city and rescue thousands of slaves.
Enoch is reunited with Sam, Sierra, and Jed. Jed, with an unparalleled talent for persuasion, is King of Camelot. When negotiations for an alliance fail, Enoch must surrender to his mentor and oldest brother, or risk making a powerful enemy.
Arkade, Hayley, Hayven, Jacob, and Aja defend the city of Boise against wizards, dragons, and the Syndicate, a united organization of mercenaries, pirates, and street pharmacists. The Syndicate has been abducting thousands of men, woman, and children, and selling them in Agartha for a dark purpose. While pursuing the slave caravan, the companions lend help to the besieged cities of Twin Falls, and the Crystal City.