 The Covenant are a fictional theocratic military alliance of alien races who serve as the main antagonists in the first trilogy of the Halo video game series . They are composed of a variety of diverse species , united under the religious worship of the Forerunners and their belief that Forerunner ringworlds known as Halos will provide a path to salvation . After the Covenant leadership — the High Prophets — declare humanity an affront to their gods , the Covenant prosecute a lengthy genocidal campaign against the technologically inferior human race . 
