The Sangheili are a saurian sapient species known for their warrior culture and combat skill. Named after their home planet, Sanghelios, they have historically been known to humans as Elites for their former role in the Covenant's military hierarchy. Originally one of the Covenant's two founding species, the Sangheili formed the hegemony's military backbone until just before the end of its existence. They had a very strong rivalry with the Jiralhanae, which finally led to genocidal violence during the Great Schism at the conclusion of the Human-Covenant War.
After the High Prophets Truth and Mercy ordered the genocide of the entire Sangheili race during the Great Schism, the species was forced into civil war against the Covenant proper. This was established after the assassination of the High Prophet of Regret at the hands of John-117. The two remaining Hierarchs held the Sangheili responsible for the Prophet of Regret's death, and the species was seen as "unfit" to continue to guard the Prophets. The Prophets sought to achieve this through the use of the other Covenant races, primarily the Jiralhanae. Consequently, the Sangheili led a rebellion against the Prophets. A significant number of Sangheili sided with the UNSC against the Prophet-led Covenant; this alliance continued to hold in the post-war era. The Great Schism formed the bedrock of the Covenant Empire's ultimate collapse and the end of the Human-Covenant War.
In the post-war years, the Swords of Sanghelios, led by Arbiter Thel 'Vadam and a grand council of kaidons, emerged as the effective Sangheili government. However, they were opposed by multiple Sangheili factions with differing ideals of how to build a future for their civilization, which resulted in the opposing Sangheili factions leaving Sanghelios in search of Covenant remnants to join while the remaining Sangheili continued hostilities with Jiralhanae groups.
Sangheili are physically imposing beings, typically standing more than a foot taller than the average human. They are vaguely reptilian in overall appearance, with leathery skin, digitigrade legs, and sharp claws and teeth. Their large hands have two fingers and two thumbs. Their most distinguishing trait is their jaw structure, which is made up of four separate mandibles attached to their face.
Sangheili are intelligent, agile, and extremely strong, and are often characterized by their bravery and honor. Sangheili warriors augment these natural abilities further through use of energy shields integrated into their armor. Depending upon rank and mission objective, they are commonly seen in battle with plasma rifles, carbines, needlers, needle rifles, along with their cultural signature weapons, energy swords. Sangheili employ coffin-like orbital insertion pods as well as Spirit and Phantom dropships for military transit purposes and rapid-response operations.
Historically, Sangheili have followed the Covenant mentality of maintaining hatred towards humanity, believing them to be an affront to their religion and a challenge towards the Great Journey. However, many Sangheili were able to put this animosity aside when an alliance of Sangheili joined the UNSC during their expedition to the Ark. After the Human-Covenant War, many Sangheili are still distrustful of humanity and some participate in terrorist attacks against them. Nonetheless a large number of Sangheili, most notably those loyal to Thel 'Vadam, have attempted to form steady alliances with their former enemies, as well as improving relations with other former Covenant species such as the Unggoy and Jiralhanae.
Sangheili are muscular and very tall, usually standing between 7.38 and 8.6 feet, although they often seem slightly shorter due to their usual hunched position, but the armor they wear makes them appear more hunched than they actually are. Their jaws are quadruple-hinged, with an upper jaw and four lower mandibles arranged in two tiers. Mandible and upper jaw structure along with teeth shape and numbers result from different phenotypes, but they do not indicate reproductive isolation. These mandibles have between six and twelve teeth each, and some Sangheili have an additional, larger fang on the tips of each mandible. Anywhere from eight to more than a dozen broader teeth may be mounted on the upper jaw structure. Adult Sangheili mandibles can be found in varying shapes, sizes, and ranges of dexterity, and are as distinctive as a human fingerprint. Some Sangheili also possess molars. Sangheili smell with the use of two nostrils, each slightly in front of and below the eye socket. Given their predatory nature, a Sangheili's sense of smell is likely very developed. Despite the Sangheili jaw structure, they are able to pronounce the letter "M" without difficulty, a fact that human scientists have been unable to explain. They do, however, have difficulty pronouncing "P". For example: Dr. Evan Phillips, one of the foremost human Sangheili experts, was addressed as and referred to as "Phillisss". Additionally, the Sangheili skull has a density sufficient enough to prevent a .40 caliber bullet from being able to exit the other side upon impact.
Their hands are tetradactyl, each having two fingers in the middle and an opposing thumb on either side. Contrary to what their anatomy might suggest, Sangheili could release a loud, sharp and piercing whistle by placing their thumbs on the same hand into their mouths and blowing through the narrow gap. Their legs are digitigrade, with short upper and lower legs, and elongated tarsals, using the distal and intermediate phalanges to support their weight when walking. This arrangement possibly allows them to run very quickly and jump large distances, compared to ordinary humans and other Covenant races. Their superior agility may also be attributed to their home worlds higher gravity; the additional strength required to move normally in a high-gravity environment would likely cause them to be more powerful in lower gravity situations. They also appear to have a double set of pectoral muscles, which contributes to their incredible strength. On the other hand, their digitigrade stance makes it difficult for them to climb vertical constructs such as ladders. The Sangheili have 241 bones and ten pressure points, with two of them being the neck and the chest.
Sangheili have a binary circulatory system that pumps indigo-colored blood possibly showing a manganese base. They breathe oxygen and their home world has a nitrogen-oxygen atmosphere comparable to Earth's, allowing them to breathe the same atmosphere as humans. Sangheili cannot breathe molecular nitrogen. Sangheili have a similar digestive system to that of humans. They are shown to have an esophagus and intestines, and are also depicted to have an anus.
Most Sangheili have leathery skin covered in many part by scales. Young Sangheili have pale protective scales hanging from their necks that they lose with age, an evolutionary leftover from the days when Sangheili parents used to carry their offspring in their jaws. Sangheili skin color can range from light brown to dark brown, light gray to black, and blue. They have forward-facing eyes with vertical slits and horizontal eyelids much like those of terrestrial reptiles, likely giving them high-resolution central vision and depth perception. Their eyes can have multiple colors ranging from red all the way to green and can be even gray. Most Sangheili, however, have yellow or orange eyes.
Sangheili exhibit minor sexual dimorphism, with the females being slightly smaller than the males. Sangheili males possess a subtle leathery scent, while females have been described as smelling like "clean feathers". Sangheili are oviparous, meaning that they lay eggs rather than giving live birth. They incubate their recently hatched young in tank-like pods. The species is remarkably long-lived; Sangheili over 60 or 70 years of age have shown to be fully fit for combat duty, and Jul 'Mdama was considered young, at least in keep elder terms, at 64 years old, Thel Vadam was considered to be one of youngest Sangheili to not only be promoted to Shipmaster but also one of the youngest Sangheili to achieve the title of Supreme Commander between his late 40s to early 50s while by 851 BCE, 'Crecka was over 90 years old. Nizat 'Kvarosee was stated to have served in the Covenant for roughly 200 human years. Circa 100,000 BCE Sangheili life expectancy was 27 Earth years. This discrepancy was likely due to their primitive culture at that time having little, if any, function medicine, whereas Sangheili of the 26th century have medicine and medical technology surpassing humanity.