Unggoy Ultra is the highest known Unggoy military rank.
Grunt Ultras can sometimes be seen commanding groups of lower class Grunts in battle, and are even seen leading black-armored Special Operations Grunts into combat, and it is rare for the player to encounter them when playing on lower difficulties, such as Easy or Normal (without the Thunderstorm Skull activated).
Unlike Elite Ultras, Grunt Ultras do not appear to have absolute authority over other Covenant units. It is quite common to encounter two or three leading a small group of Grunts, yet the Elites (or Brutes among the Loyalists) are ultimately in complete command; in the same way that even minor Prophets outrank Sangheili Ship Masters, Grunt Ultras are inferior in rank to even Sangheili Minors.
These Grunts, like their lower-ranking cousins, appear in groups. They are very intelligent, making as few tactical errors as a Sangheili Major. They usually display even more bravery in combat than a SpecOps unit, and are more often used for specialized attacks, rather than standard military operations.
Unggoy Ultras usually throw more grenades and are far more accurate and deadly at a greater distance than the lower ranked Unggoy Majors and Minors. They also wield Needlers with greater frequency than their subordinates, though it is still common for them to use Plasma Pistols. They can take the same amount of damage Spec Ops Grunts do (more than three times as much as a Grunt Minor can), but they are still vulnerable to headshots (even though it may take more than one for lower power weapons). In Halo: Reach the helmet of the Ultra Grunt protects them from the first headshot, after which it will fall off. Like SpecOps Grunts, they are rarely caught sleeping on duty. They still panic if they know that they are being overwhelmed, but are more likely to go berserk than run away - especially if one of their comrades was killed by a grenade. An Unggoy Ultra, compared to an average Unggoy Minor, can take much more damage and usually takes two to three melee attacks instead of one to be killed, even on Normal difficulty.
The purpose of this rank designation has been generally unclear. They were first mentioned in Halo: First Strike, pushing carts of cleaning fluid, demonstrating that they still hold very low positions despite the title of "Ultra." However, they were also seen inside the Scarab walker in New Mombasa along with high-ranking Elites (Minor, Major, and Ultra). They were also seen throughout New Mombasa, Delta Halo and Cairo Station. This led some to believe that they were "technicians" or engineers (not to be confused with the Engineer species) of some sort, but the production book, The Art of Halo, confirms that they outrank Grunt Majors. It has, however, been suggested that white armor actually signifies manual labor, while the more silver armor signifies Ultra. Still, there is not a sufficient color difference to make this a significant case. It is likely that even though they are high-ranking Grunts, they are not free from manual tasks.
The rank is a rare achievement for an Unggoy, due to the fact that the species has a high death rate. Grunt Ultras most likely command a great degree of respect from the Grunts under their supervision, as their combat prowess must be exemplary...or they are just extremely lucky.
- Sometimes an Unggoy Ultra's armor appears slightly darker, possibly meaning that they have more experience than standard Ultras.
- If one plays Halo: Combat Evolved with an unsupported video card, but has at least 32 MB of video memory, all armor colors will be white, with some exceptions such as the Mgalekgolo - which has led to some fans believing that all Unggoy in Halo: Combat Evolved are Ultras. However, white is the basic color of all models in the Halo: Combat Evolved engine. The models are rendered with no specific color until selected by an algorithm that would determine which Unggoy variant to spawn, determined by the difficulty level (meaning higher difficulties are more likely to spawn Unggoy Majors). There is a degree of randomness involved, as the player may notice an Unggoy Minor in one location, die, then realize it is actually an Unggoy Major.
- More Grunt Ultras seem to have supported the Covenant Loyalists, as seen in the Halo 2 level High Charity.
- Ultra Grunts never appear in Halo 3, contrary to popular belief. They are replaced by Spec-Op Grunts. Initially, they were thought to be Ultra Grunts, since they had similar color armor, but the Bungie.net tracking system consider them as Spec-Op Grunts.
- In Halo: Reach, Unggoy Ultras seem to have a better understanding of their weapon, such as making use of the overcharge feature of their plasma pistol.
- In Halo: Reach, Ultras have a cylindrical methane tank and a full face mask. The shape of the methane tank appears to have been influenced by early concept art for Halo: Combat Evolved, and designs later seen in the Halo Graphic Novel, Halo: Uprising, and Halo Wars. They have been nicknamed "Keg Grunts" by Bungie due to the shape of the methane containers.
- In the carnage report in Halo: Reach, Unggoy Ultras are referred to as "Grunt Heroes."
- In Halo: Reach, the Unggoy Ultra's masks protect their head, which allows them to survive a headshot once, giving the mask better ballistic properties than MJOLNIR helmets and those worn by Sangheili.
- This full helmet also allows them to survive in a vacuum as seen in the level Long Night of Solace.
- Their helmet may also be a reference to the Halo: Combat Evolved and Halo 2 Grunt helmets.
- Though Grunt Ultra is the highest Unggoy rank, Elite Minors still seem to outrank them, since they have no control of other species but Unggoy, although this should not be considered odd because of how low the Unggoy species is in social ranking in the Covenant.