Set in 2559, decades after the crew of the human warship Spirit of Fire vanished into uncharted space, the ship and its cryo-sleeping crew awaken at the Ark, a colossal Forerunner installation capable of building the galaxy-threatening Halo rings. There they find a ruthless new enemy already entrenched: the Banished, a savage mercenary faction led by the cunning Brute warlord Atriox that rose from the ashes of the collapsed Covenant. Under Captain Cutter's command, the outnumbered and outdated UNSC forces must marshal their soldiers, Spartans, and war machines to wrest control of the Ark from the Banished and stop Atriox before he seizes its terrible power.