Covenant

The Covenant is a religious cult of alien races ruled over by the Prophets and enforced by the Elites and Brutes. However, civil war broke the Covenant in two and the Elites rebelled, taking the majority of the Covenant Military force with them.

The Evil Prophets were destroyed by the combined Human-Elite-Reaper forces, and the leader of the Covenant, The Prophet of Truth, was killed by the Arbiter.

The Covenant used to hate humans, and even declared war on them. This conflict became known as the Human-Covenant War.