when sheperd uses the J relay, he finds that the alince isn't the only humans around. when sheperd teams with Peti-oficer/Sparten Brock Maran, they find a prothein becon, but the covanent and geth have teamd to gether after they create a new relay to halo

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