Lekgolo

The Lekgolo (Latin Ophis congregatio, meaning "Assembly of snakes") are a species of small colonial worm-like creatures that can join together to form purpose specific assemblages, such as Mgalekgolo, commonly referred to by humans as Hunters. Lekgolo are also able to integrate themselves into machinery such as the Scarab and use their combined intelligence to pilot, or control, the vehicle or machinery.

Every worm-like creature is an individual eel, about 1.4 meters long, with its own central nervous system. It is speculated that the Lekgolo have microscopic muscular cilia which are used to connect to other Lekgolo and that each cilium is capable of communicating chemically similar to a synapse, explaining how the species can become a collective being in the form of the Mgalekgolo.

History
The Lekgolo evolved on their homeworld of Te and fed by burrowing through the ground of their planet. They first came into contact with the Covenant when the then young alien collective landed in search of Forerunner artifacts. They found only the destroyed remains of a Forerunner space station which had once contained many relics, but was now bare due to the actions of the worms, which had broken down and eaten the devices. The San 'Shyuum  viewed this as heresy, and declared war on the Lekgolo in what would later be called the Taming of the Lekgolo. Covenant fleet commanders soon found that indiscriminate destruction would have unacceptable consequences, however: since the Lekgolo lived in the sacred relics that the Sangheili  were trying to preserve, simply annihilating the Lekgolo would have resulted in the destruction of some or all of those relics. The Arbiter that was created during this crisis suggested that they could be tamed and put to better uses as part of the Covenant Hierarchy.

Thus, those Lekgolo colonies which preserved Forerunner relics were incorporated into the Covenant, while those that destroyed relics were eradicated. This extermination campaign proved to be difficult, as the Lekgolo were able to combine into powerful Mgalekgolo; consequently, the Lekgolo won most, if not all, ground engagements. The Covenant's forces were completely overwhelmed by the sheer size and ferocity of their foes. On the verge of defeat, the Covenant took desperate measures, threatening to orbitally bombard the planetary surface of Te unless the Mgalekgolo surrendered.

In 784 B.C.E., the Covenant absorbed the Lekgolo incapable of consuming Forerunner relics into their ranks and eradicated the colonies which had caused harm to the Forerunner relics in orbit. The Mgalekgolo gestalts were later given thick armor plates and Assault Cannons to help them serve the Covenant as shock troops.

During the Great Schism, the species was divided between those that supported the Covenant Loyalists and those that supported the Covenant Separatists, though it is thought the majority supported the Separatists given their loyalty to the Sangheili.