Following the birth of the Covenant, the new Sangheili-San'Shyuum coalition explored the galaxy searching for Forerunner artifacts — and along the way encountered several species that they would come to integrate into the alliance.

In our last Halo timeline article, we explored the bloody, brutal background of the war between the Sangheili and the San'Shyuum, and the formation of their alliance, the Covenant.

In this installment, we're going to take an in-depth look at the history of the Covenant's expansion throughout the Milky Way galaxy, and the conquest of all of the species that would become integrated into the caste system of the Covenant.

Prelude: The Covenant divides and conquers

Covenant fleets began to comb the Milky Way galaxy for any Forerunner technologies.

Following the ratification of the Writ of Union, the Covenant began their quest to discover (and claim) the Halo rings and any other Forerunner artifacts. Fueled by the prospect of the Great Journey — an event believed to happen when the Halo rings are activated, propelling all of the Covenant to salvation — the Sangheili and San'Shyuum took to the stars. For decades, the coalition expanded uncontested, moving from world to world, taking any Forerunner technology available, often by force. However, the Covenant would eventually be met with their first real challenge.

784 Before Current Era (BCE): Taming of the Lekgolo

The Lekgolo species proved to be extremely proficient in ground combat.

Sixty-eight years after the Sangheili-San'Shyuum alliance began, the still-young Covenant encountered their first formidable adversaries in the Lekgolo.

Upon arriving at their homeworld of Te, the Covenant discovered that the Lekgolo frequently ingested Forerunner materials for their mineral contents. Enraged at the prospect of eating the buildings created by their gods, the Covenant declared that the Lekgolo species were heretics and that they needed to be exterminated.

This was easier said than done, however. Upon landing on Te, the combination of the planet's heavy gravity and the huge forms of the Lekgolo made conducting a ground campaign against them extremely difficult. As a result, the engagements between the Sangheili military and the Lekgolo often ended in stalemates or defeat for the Sangheili.

During his time on a moon of Te, the then-current Arbiter discovered that the Lekgolo was a worm species.

Unsure of how to proceed, the San'Shyuum sent a special type of Sangheili warrior called an Arbiter to investigate one of Te's Lekgolo-controlled moons, and to study the species' strengths and weaknesses. This Arbiter spent an entire year studying the Lekgolo; during his observations, he realized that the Lekgolo were not individually large. Rather, the Lekgolo were, in fact, each small, sentient worms that could combine to create hulking masses for combat purposes.

Upon his return, the Arbiter suggested that the Lekgolo would prove useful as allies. Wishing to integrate them into the Covenant, the San'Shyuum offered them a place within the Covenant empire. Refusal would mean that the fleets of the Covenant would burn Te into ash from orbit. Faced with no choice, the Lekgolo accepted the offer.

The Lekgolo species would come to be regarded highly in Covenant society over time. Both the Sangheili and the San'Shyuum found them to be impressive creatures, with the Sangheili admiring their capacity for combat, while the San'Shyuum tasked them with integrating with the systems of Forerunner technology and Covenant machinery. When several Lekgolo come together as a large form and are equipped with their armor and fuel rod cannons (as you see them in the games), they become known as Mgalekgolo.

1112 Current Era (CE): Conquest of the Yanme'e

The Yanme'e species make excellent airborne infantry due to their fast speeds.

After almost a thousand years of continued conquest and expansion, the Covenant discovered the Yanme'e on the world Palamok, which was home to Forerunner relics. When the Covenant attempted to land and take these relics, the Yanme'e became hostile, attacking ferociously. While the skilled Sangheili and mighty Mgalekgolo were more organized and effective soldiers, both sides ended up taking heavy casualties due to the sheer number of Yanme'e.

The San'Shyuum, meanwhile, had discovered a way to communicate with the Yanme'e, and soon after, both parties came to an agreement in which the Yanme'e would join the Covenant's ranks. Like the Lekgolo, the Yanme'e became highly regarded in the Covenant's caste system; Yanme'e were incredibly effective airborne infantry, but they also served the Covenant by fulfilling the role of machinery maintenance.

1342 CE: Pact with the Kig-Yar

The Kig-Yar were skilled marksmen and also frequently engaged in piracy.

Around 200 years, following the integration of the Yanme'e into the Covenant, the pirate species known as the Kig-Yar was discovered on its homeworld of Eayn by the Covenant empire. Though they initially resisted, the avian species knew that the Covenant military was too powerful to possibly hope to defeat. As a result, the Kig-Yar accepted a Covenant offer to be allowed to live in exchange for their services in the Covenant as mercenaries.

Because of their strong eyesight, Kig-Yar made excellent snipers and also served in the Covenant army as defensive infantry units, utilizing a wrist-mounted plasma shield. Despite this, both the Sangheili and the San'Shyuum found their practices of trickery and piracy distasteful. As a result, the Kig-Yar was located very low in the Covenant caste system.

2142 CE: Enslavement of the Unggoy

The Unggoy was completely defenseless to the might of the Covenant.

After 800 years passed following the Kig-Yar's joining of the Covenant, the Unggoy species was discovered on the icy planet of Balaho. After observing the Unggoy, the Covenant quickly determined that they would make excellent slaves and cannon fodder. The Covenant landed on the planet only to find that the Unggoy offered no resistance. As a result, they were rounded up like sheep and brought into the Covenant by force. Due to their nature as slaves, the Unggoy were extremely low regarded in Covenant society, even more so than Kig-Yar.

The Unggoy Rebellion

The Unggoy proved that they could be formidable warriors.

The Kig-Yar, in a cruel act of sabotage, poisoned Unggoy food and caused many male Unggoy to go sterile in the year 2462 CE. Angered by this, the entire Unggoy species began to rebel against the Covenant. This uprising would be known as the Unggoy Rebellion.

Due to their sheer numbers, the Unggoy proved to be a problem for the Covenant military. While they weren't skilled in battle, the masses upon masses of Unggoy often proved to be too much for the Covenant military to handle. The San'Shyuum named a new Arbiter to handle the situation, and in a desperate act, he began to bombard Balaho with Covenant fleets from orbit, hoping to dissuade the Unggoy from continuing their rebellion.

This plan worked; the Unggoy quickly ended their violent spree. The ferocity of the Unggoy in this conflict had not gone unnoticed, however. The Sangheili, praising them for their courage and tenacity in battle, rewarded them with better training and equipment, even allowing them to fight alongside the other military species. Because of this, the Unggoy had elevated their rank within Covenant society, equal to that of the Kig-Yar.

2492 CE: The integration of the Jiralhanae

The Jiralhanae were considered savage by most members of the Covenant's society.

Thirty years after the Unggoy Rebellion, the Covenant discovered the Jiralhanae species on their homeworld of Dosiac. Then engaged in a civil war, and they were considered easy targets for the Covenant. While ferocious and vicious warriors, the Jiralhanae were unorganized and primitive; as a result, the Covenant's advanced, highly-trained military easily defeated and conquered the species.

Used mostly in shock trooper roles, the Jiralhanae are ranked below the Lekgolo, equal with the Yanme'e and above the Unggoy and Kig-Yar. The Sangheili harbor a particular distaste for them, seeing their style of fighting and their culture as barbaric and dishonorable.

Your thoughts

What do you think about the expansion of the Covenant empire? Do you have a favorite species in the Covenant? (Mine is easily the Sangheili!)

If you haven't already, catch up on our previous Halo timeline stories, listed below. And then let us know how you feel in the comments.