After drifting through deep space for decades in cryogenic suspension, the crew of humanity's warship Spirit of Fire suddenly reawakens at the Ark, an ancient and colossal Forerunner megastructure with the power to construct civilization-ending Halo rings. They arrive to find the installation already claimed by the Banished, a fierce mercenary army born from the Covenant's collapse and commanded by Atriox, an ambitious and fearless Brute leader determined to unlock the Ark's devastating capabilities. Faced with an enemy force that vastly outnumbers their outdated military assets, Captain Cutter must rally the UNSC's remaining soldiers, elite Spartans, and armored war machines in a desperate struggle to reclaim the installation and prevent Atriox from wielding its world-ending technology.