The Covenant Empire, also referred to as the Covenant, was a theocratic hegemony made up of multiple alien species that maintained control over a large portion of the Orion Arm in the Milky Way galaxy. The Covenant was a political, military, and religious affiliation, originally a mutual alliance between the San 'Shyuum and Sangheili following a brutal conflict between the two warring races. Its expansion to include at least six other races united in the worship of the Forerunners and the Halo Array soon began after the original formation.
The Covenant waged a genocidal campaign against humanity, until they were formally defeated due to many factors - the most crucial of which was an internal conflict. Whilst the Covenant's leadership was either lost during the Flood infection of High Charity or during the Battle of Installation 00, the Covenant continues to exist even after the conclusion of the war. A splinter faction of Sangheili loyalists remains known as the Covenant Remnant; this terrorist group is deemed hostile to Humanity, breaking the truce formed at the end of the initial war with the Covenant. They have been seen to field large numbers of warships, but their true power, and indeed the number of Covenant involved with their activities, is unknown.
It is also unknown in what capacity the other parts of the Covenant continue to exist, or even if any other fragments of this once-great empire remain.