As Master Chief defends Earth against the Covenant forces, the Office of Naval Intelligences "Section Three" has devised a plan to give the UNSC vital time.

The planet Onyx is virtually abandoned and the perfect place to set this new plan in motion. But when the Master Chief destroys Halo, something is triggered deep within Onyx: Ancient Forerunner technology stirs, and fleets of UNSC and Covenant race to claim it to change the course of the Human-Covenant War.

But the reawakened and ancient force may have plans of its own...