2559. It has been a year since the rogue artificial intelligence Cortana seized control of the Domain, an otherworldly dimension housing a vast information network. With an array of Forerunner weapons at her disposal, Cortana set out to enforce an authoritarian peace on the civilizations of the galaxy. But as the United Nations Space Command flagship Infinity prepares to strike against Cortana at Zeta Halo, another plan has also been set in motion.

An ancient access point hidden on a seemingly insignificant human colony has become the focus of a parallel effort to claim the Domain and its immeasurable capabilities. The UNSC, however, needs a key: a living, forsaken product of an old war. As a new generation of heroes rise to meet this challenge, and Cortana's pursuit of control reaches a desperate and sudden crescendo, a cunning, ruthless warrior emerges from the shadows of the Banished, who has vowed to fill the new power vacuum by any means necessary...