It has been over six months after the UNSC was defeated in battle over Halo Installation 07. The Master Chief, having disposed of Escharum and yet another new threat, the Harbinger of Truth, ventures to the crash site of the UNSC Infinity with his new companion, in the hopes of finding an unknown weapon, powerful enough to have killed Cortana, before the now scattered Banished do.

10 million years before the creation and firing of the Halo Array, to starve the greatest threat in the known galaxy into obscurity, a lone Precursor, a member of the esteemed court that had seeded the galaxy with life and purpose, bears witness to the consequences of his actions, and to what extent his creations would go to obtain control of the Mantle of Responsibility.