The Unggoy (Latin, Monachus frigus, meaning "cold monk"), or Grunts as they referred to by humans, are the lowest-ranking member species of the Covenant Empire.
They are the only Covenant species to breathe methane, rather than oxygen and as such, they must wear large methane tanks on their backs and breathing apparatus in order to survive on other planets and in most areas on board Covenant ships.
What the Grunts lack in individual skill or strength, they make up for with overwhelming numbers due to their high breeding rate. Because of this, in combat situations they are primarily used as cannon fodder.
The Unggoy obey other races of the Covenant more out of fear, than political or religious conviction. Their faithfulness is further enforced by the threat of punishment, and although they're known to panic and flee once their commander has been eliminated, it will occasionally manifest itself as a suicidal attempt to eliminate the enemy forces.
Their simple nature makes them best suited for menial work, so in addition to manual labor, they are often tasked with monitoring space for signs of human communication. As a result, most Grunts have a working knowledge of two or more Human languages. This has become a source of pride for them. Unggoy enjoy trading human communication files, such as soap operas and comedies, through their black market.
Balaho, the Unggoy homeworld, was devastated by the collapse of its biosphere due to massive global over-industrialization that occurred even before the activation of the Halo Array. While there are indications that the Unggoy society had once reached Space Age, by the time of their discovery by the Covenant they had yet to return to such a state. In the 100,000 years following the activation of the Array, their civilization only managed to enter the Industrial Age.
Grunts were integrated into the Covenant around 2142 CE (about 410 years prior to the events of Halo: Combat Evolved). They are one of the later races to be introduced into the Empire.
They are known to be bitter rivals with the Kig-yar (Jackals), with whom they share the very bottom of the Empire's social hierarchy. The breaking point came when the High Council refused to investigate the matter of a junior staffer in the Ministry of Concert discovering evidence of a Kig-yar plot to poison recreational narcotics the Unggoy enjoyed, which would render them sterile.
The rising tensions with the Jackals and the general disinterest from the other Covenant races led to the Grunt Rebellion in 2462, or the 39th Age of Conflict. While the rebellion was ultimately put down through the use of an Arbiter and the near-glassing of the Unggoy homeworld, the Grunts managed to prove that they were not the cowards they were perceived to be. The Sangheili (Elites) managed the rebellion quickly, but in the end rewarded the Grunts for their courage and warrior spirit by returning them to the ranks of the Covenant, this time as weapon-carrying infantry.
Despite rising in the ranks of the Covenant Army as result of the rebellion, they still had next to no political power in the Covenant; the highest political rank available to an Unggoy was Deacon, a religious role of the lowest rank in the Ministry of Tranquility.
When the Great Schism began and the Covenant Civil War broke out, the low rank of the Unggoy was one of the factors that led to their lack of political loyalty, as the Grunts did not ally with either side and stayed with whoever commanded them.
- Unggoy means "monkey" in the Filipino language Tagalog.
- Grunts are often voiced by Bungie writer and cinematics director, Joseph Staten.