Covenant Empire (Halo Movies)

Covenant Empire was a theocratic hegemony in the Halo movies. It is made up of multiple alien species that maintained control over a large portion of the Orion Arm in the Milky Way galaxy and was a political, military and religious affiliation, waging a genocidal campaign against humanity and worshipped the Forerunners and the Halo Array.

San Shyuum
The highest caste, the San Shyumm or Prophets, lead the Covenant and exert control over all religious and political affairs. Though physically weak, Prophets wield power through absolute command of the Covenant and through scavenged Forerunner technology, leaving conquest to the other races. Their higher understanding of the Forerunners gives them great ego and religious influence over the Covenant.

Sangheili
The second highest caste; Sangheili or Elites, served as the military leaders of the Covenant before the Great Schism in 2552. While Prophets often had the final say, it was the Elites who organized military campaigns and naval engagements. They maintain the military structure of the Covenant and ensured the Prophets' orders were followed, as well as their own. Elites consider the other client races to be below them in every way and are the only race permitted to build and operate starships. Elites are separated into ranks based on skill and experience and to advance in rank, they must earn honorably earn such achievements on the battlefield. They were a major component and were the only caste able to maintain the military hierarchy as well as having a voice within the High Council.

Jiralhanae
Jiralhanae or Brutes were one of the newer species to the Covenant and are the only race that obtained a very close equal status to the Elites. They have an incredible resilience to damage due to their tough hides and use a number of weapons and vehicles based upon their pre-Covenant technology. Brutes always work in packs of 3-8 when possible and eventually took over the role as personal bodyguards of the Prophets and the backbone of the Covenant military.

Huragok
Huragok or Engineers are actually an artificial species created by the Forerunners.