The Ninth Age of Reclamation is over. The Covenant, along with its member state of the Alliance serving Humanity, have become a part of Citadel space. A special operations soldier, Shepard, will find herself thrust forward into an epic race against time.

The Wall cascades, as two inquisitive Humanities tamper with that which they should not. And in the hollow space between universes, like a rats in the walls of a house that they build themselves, entities watch. Halo/Mass Effect