Unggoy

The Unggoy, nicknamed Grunts by the UNSC, are a sapient species and one of the former client species of the Covenant. The Unggoy occupied the lowest tier in the Covenant's caste system, and comprised the majority of the hegemony's labor force as slaves or serfs; consequently, they are near-ubiquitous across the Covenant sphere. While the Unggoy had some means of social mobility, either in special laborer duties, as merchants or in the clergy, few individuals were fortunate enough to have such opportunities.

Prehistory and rise of civilization
The evolutionary and pre-Halo history of the Unggoy is a difficult one to piece together, as the Forerunners kept few records on the species, and none of these go into any depth about what their society was like. As a result, most of what is known is based on speculations from human xeno-biologists and xeno-anthropologists, who are forced to look for evidence of their past in their anatomy and behavioral quirks.

The most readily-accepted theory is that the Unggoy evolved from a genus of amphibious primates. Early prehistoric individuals led tribal societies, and sustained themselves through hunting small animals and scavenging the corpses of larger ones. It is generally held that they were an important part of their ecosystem, where they were preyed on by Balaho's apex and second-order predators due to their numbers and considerable size. These often-unstoppable threats drove a number of early migrations outside of their home continent, while those that remained invented the defensive weapons and tactics they needed to survive. Over the centuries, this manifested in an instinctual fear of nature and anything that didn't resemble an Unggoy. Because of this, the history of their civilization was permeated with massive deforestation and culling campaigns, replaced with homes for their rapidly-expanding population. By the time of the Forerunners, little of the original wildlife and natural scenery remained.

They would reportedly develop themselves into a Tier-4 civilization by Forerunner metrics, where they enjoyed limited access to spacefaring craft. However, centuries of habitat destruction, over-industrialization, and pollution would lead to a massive environmental collapse, killing most of the animal and flora supplies that fed the massive population. The damage was only mitigated by the intervention of their Forerunner overlords, who implanted massive atmospheric processors and hydrosphere filters to stabilize Balaho's condition, and supplied alternative food sources. This was the end to their assistance, as the escalating Flood invasion saw them leave the Unggoy to deal with the problems themselves. By the time the Halos fired, they were still unable to meaningfully restore their homeworld's ecosystems.

The Covenant
The first Covenant scouts would discover Balaho in 238 BCE, at a time where limited-scale industrialization was rediscovered among certain tribes. The surveyor's reports of a hardy but intelligent species that were eager to be taken off-world were initially treated with little fanfare. Their small numbers, low native technology level, peculiar native atmosphere and their consequent reliance on a methane supply outside it, initially makes them of little interest to the Covenant. As such, they are made a vassal-species, but no concerted effort is made to integrate them to the Covenant hierarchy, also partly due to the Covenant itself going through a minor interregnum at the time. By this point, the Covenant's conversion process has not yet fully solidified, and there is debate as to whether such lowly and primitive beings are even eligible for Salvation.

Over the subsequent centuries, the Unggoy begin to spread across the Covenant Empire, first as curiosities, entertainers and status symbols for wealthy magnates and nobles, then, more widespread servants and slaves. Increasing numbers of Sangheili aristocrats and warlords begin to foster Unggoy colonies as serfs as well as cannon fodder in their clan wars. Gradually, the Unggoy become embedded in the Covenant's power structure. Eventually, the usefulness of the species is re-evaluated, and the High Council takes steps toward a proper conversion process. Scores of Ministerial officials and missionaries are assigned to study the Unggoy, reassess their worthiness of the Great Journey, and convert them to the Covenant faith and way of life. By this point, many of the Unggoy have already accepted the Covenant religion, mostly with open arms due to the appeal of its message of universal salvation. They were formally elevated to the status of full signatory client-species in 214 CE, and would be the second race to be assimilated following the Writ of Union.