A new threat faces the world of Erdas in this continuation of the New York Times bestselling series.

Something ancient and evil has awoken from beneath the world of Erdas. Shrouded in shadow and older than memory, just a sliver of its power can destroy with a touch. Even the spirit animal bond, the sacred link between humans and animals that keeps Erdas in balance, is under threat.

Four young heroes, Conor, Abeke, Meilin, and Rollan, are determined to stop it. Together with their spirit animals, they embark on a desperate journey that takes them deep underground and to the far corners of the world. As friends and allies fall around them, the four have no choice but to push forward and confront this darkness. If they stop to look back, they'll see the truth: Evil already has them surrounded.