The Prometheans were the highest and most respected group of Warrior-Servants in the Forerunner ecumene. During and after the Human-Forerunner War, they were led by the Didact. During the Forerunner-Flood war, the Prometheans' main base of operations was the fortress world known as Requiem. Elements of the Prometheans survived the Forerunner-Flood war and the activation of the Halo Array, eventually awakening within Requiem and rising to oppose the UNSC in 2557.


The Didact is a Forerunner Promethean who held an extremely high status in the Forerunner society as supreme commander of the entire Forerunner military. He wholeheartedly believed in the Mantle the Forerunners held to protect life, and initially opposed the Halo Array as a sin beyond measure. He was also the lover and husband of the Librarian, and the one who eventually activated the Halo Array. Following this, he was exiled in a Cryptum on Requiem, awakening in 2557 and rising to oppose humanity, the descendants of his ancient enemies. Originally thought to have been physically killed by the former Master Builder Faber, the Didact effectively existed as two individuals during the final days of the Forerunner-Flood war; his original self, as well as his implanted consciousness within a young Forerunner known as Bornstellar Makes Eternal Lasting. To differentiate these two incarnations, the original Didact was referred to as the Ur-Didact, while his other incarnation was known as the Bornstellar-Didact. The Didact was considered in his time to be the supreme enemy of humans, viewing mankind as a grave threat and considering them to be extremely contentious, bigoted and self-centred. However, this animosity was not driven by hatred or malice; rather, it was a largely rational reaction to humanity's actions. On the other hand, he also respected humans as warriors and regarded them as honorable, unlike their San 'Shyuum allies who had surrendered earlier in the war. This was demonstrated when he met with his main opponent, Forthencho, the Lord of Admirals, in person after the humans' defeat, speaking to him as a fellow warrior and reassuring him about the future despite humanity's grim predicament. He also understood humanity's motives for aggressive expansion after studying their records of their struggle with the Flood. Nonetheless, he felt it necessary to eradicate the contemporary human civilization entirely to ensure they would not rise to challenge Forerunner dominance again. The Didact's antipathy toward humans was at least partially curtailed by the Librarian, who was, in contrast, regarded as humanity's greatest protector. It is likely, however, that his opinion of humanity has changed little as of the present, and indeed it can be assumed he would now hold some resentment towards humanity for indirectly causing the death of the Librarian. He appeared to regard Chakas and Riser, the two humans who accompanied Bornstellar, with relative indifference, viewing them as mere annoyances, although he tolerated them because they were part of his wife's plan. By the point the Bornstellar-Didact reunited with the two, he appears to have had more of sympathy for them; he trusted Chakas enough to connect with him to Installation 07's control interface and enlist his aid in saving the ring, and later treated Chakas and the other humans gently, expressing condolence for everything they had been forced to go through. A full-rate Promethean, the Ur-Didact was a physically imposing presence. He stood approximately twice a Manipular's height and weighed four or five times as much, and had massive, heavily muscled limbs and hands with six digits. It was said that he could easily have crushed a human with his bare hands. His skin was grayish pink in colour and he had patches of bluish white fur on the top of his head and shoulders, as was common with Warrior-Servants. He had strong, serious facial features and deep-set, gray eyes. The Bornstellar-Didact was mostly similar to the Ur-Didact in appearance and stature and had a "broad, grotesque face", although upon closer examination, his comparative physical youth was apparent in his appearance. The Didact's personal armor, which bore the mottled gray and blue colors of a Warrior-Servant, was despite his lofty status considered austere in contrast to more lavishly decorated Builder armour.

Organic Prometheans

Physically, Prometheans were the highest form a Warrior-Servant could mutate to, standing around two times the height of a Forerunner Manipular and weighing about four or five times a Manipular's mass. They were heavily muscled, their hands capable of easily crushing a human. Their mental capabilities were also very sophisticated; it was common for a Promethean to share information and sensory input with the warriors under their command. Prometheans were also capable of controlling a million remote-controlled craft, such as weapon-ships, simultaneously.

They also used powerful vehicles known as war sphinxes for large-scale operations. In order to combat the parasitic Flood during the Forerunner-Flood war, the Prometheans' arsenal of weapons was specifically tailored to disintegrate biomass to prevent Flood infection. The Prometheans were responsible for creating "Warrior Keeps" known as Cryptums, where an exiled warrior could live in suspended animation for thousands of years.

Known Prometheans

·         The Didact

·         The Confirmer

·         The Grammarian

·         The Strategos

Mechanical Prometheans

The Promethean forces encountered by UNSC forces and Covenant remnant insurgents on Requiem appear to be primarily mechanical in nature, and encompass various classes of leader units known as Knights, support drones known as Watchers, and small, pack-oriented Crawlers serving mostly as cannon fodder. Noted as being "significantly different" from the original Prometheans, the origin of these Promethean constructs is revealed by the Librarian.  She reveals to the Master Chief that some of the Prometheans are humans, transformed by the Didact by means of a device known as "The Composer". When the Ecumene discovered Didact's plan to turn all of humanity into Prometheans to gain immunity to the Flood, they removed The Composer from Didact and imprisoned him in Requiem. Through her manipulation of humanity's genes, the Librarian was able to hide an immunity to the Promethean transformation in the Master Chief's genes.

Visually, unlike most Forerunner technology which is chiefly angular and geometric, these Promethean units have a more curved, almost biomechanical aesthetic. Various Promethean units, including Knights and Watchers, have distinct heads embedded in their mechanical carapaces, complete with stylized facial features; this feature was shared by the war sphinxes used by the original Prometheans. It is later revealed that the mechanical Prometheans are in fact humans who were converted into digital intelligences by the Composer following their defeat in the Human Forerunner War.

Promethean Knights are a class of mechanized Forerunner Promethean warriors. Several legions of Knights represent the central occupying force in the shield world of Requiem, alongside a number of other Promethean machines. The origins of these automatons are both ancient and mysterious. While they differ significantly from the ancient Forerunner Prometheans, a legendary class of Warrior-Servants, they are nonetheless a force to be reckoned with. They are fully weaponized, heavily armored bipedal warriors, easily capable of engaging and terminating perceived threats in almost all environments. They are known to use Lightrifles and Scattershots as their ranged armament, in addition to a bladed weapon on one hand. They are able to deploy Watcher drones, carried in the back of their armored carapace, for combat support. The Watcher sentinel can greatly improve the Knight's combat capabilities, raising hard light shields or healing the Knight, summoning Crawlers, or flinging back enemy grenades or other ordnance. Some subtypes also make use of autosentries in addition to the support that they can already summon. Upon taking critical damage, Knights completely disintegrate; their bodies erode away from where the fatal shot was received and dissolve into glowing particles. Despite this, they can be recreated and revived on-site by a Promethean Watcher. Knights have two sets of arms; two large, artificial arms at each shoulder in which the weapons are mounted and two smaller arms below the shoulders. The larger arms are composed of separate segments held in formation through an energy field. Knights also have a comparatively smaller set with small, five-fingered hands. These smaller arms are more "organic" in shape and are physically attached to the Knight's body. Knights are covered in patterns of light and have a fire-like glow around their heads. The head features an armoured helmet with glowing eyes and what appear to be grimacing jaws with rows of teeth. This helmet assembly can be retracted in two sections, revealing a glowing humanoid skull underneath.

Knight Lancers are a class of the Promethean Knights encountered by the UNSC on the shield world Requiem in late 2557. Lancers are primarily used as scouts and marksmen, as well being extremely accurate from great distances. Lancers are known for using Promethean vision to track targets, even if they are behind solid objects. Lancers are capable of teleporting over short distances; this ability allows them to enter the battlefield via teleportation or to quickly retreat during battle. Lancers are also capable of charging at their opponents in a zigzagging motion at an incredible speed. This enables them to make use of the Scattershot's effectiveness in close quarters.

Knight Battlewagons are a class of Promethean Knight encountered by the UNSC on the shield world Requiem in late 2557. Battlewagons are heavily armed and armored, serving as a last line of defense when other forces have failed. They are equipped with hard-light shielding, and are capable of deploying autonomous sentries. They use Scattershots for close-quarters combat.

Knight Commanders are a class of Promethean Knight encountered by the UNSC on the shield world Requiem in late 2557. Commanders have similar combat skills of standard Knights but instead, lead and command groups of Knights into battle. They possess stronger armor, deploy floating Autosentry turrets, and usually wield Incineration cannons.

The Crawlers are a form of autonomous Forerunner defense construct, designed by the Promethean Warrior-Servants as a means of asymmetrically combating the Flood. Crawlers are small, quadrupedal machines capable of both ranged and close-quarters combat, using a built-in Boltshot as their primary weapon; this weapon disintegrates targets to prevent their biomass from being co-opted by the Flood. Unlike the majority of Forerunner automatons, they appear to lack anti-gravity capabilities of any kind. Crawlers are ferociously aggressive, having been specifically designed to hunt down and eliminate any foreign threats, their inorganic nature making them immune to Flood infection. They travel in large packs and work together to destroy enemies by overwhelming them from every conceivable angle, relying on skirmishing tactics. Crawlers are often directed by Promethean Knights, who regard them as cannon fodder. They are protected by Watcher Sentinels, which can create new Crawlers from raw materials in the ground. In addition to the basic type of Crawler, a more heavily armed unit and a long-range unit are also employed. Numerous Crawlers were encountered by UNSC Defense Force and Covenant personnel on the shield world Requiem in summer 2557.

Crawler Snipes are a class of Promethean Crawlers encountered by the UNSC on the shield world Requiem in late 2557. Crawler Snipers appear to be more armored than the standard Promethean Crawler and are armed with a built-in Binary Rifle.

Alpha Crawlers are a class of Promethean Crawlers encountered by the UNSC on the shield world Requiem in late 2557. Alpha Crawlers lead packs of lesser Crawlers. They are distinguished from other Crawler subtypes by the array of glowing spikes on their carapaces, and are armed with a built-in Z-130 Suppressor.

The Promethean Watcher is a Forerunner Sentinel variant. Like other Promethean constructs, the Watcher was designed as a countermeasure against the Flood. Numerous Watchers were encountered on the shield world Requiem in summer 2557. Watchers are typically deployed from the armoured carapace of their Promethean Knight Commanders, assisting them with aerial combat screening and often forcing opponents to engage the Sentinel first. The Watcher is capable of healing and augmenting damaged allies, providing them with hard light shields, and can catch and return enemy ordnance, such as grenades, with a gravity-displacement field. They are also capable of summoning Promethean Crawlers to the battlefield by conjuring the Crawlers' forms from raw material in the ground. They are armed with a Boltshot, apparently built-in. The Watchers also can resurrect Knights killed in combat. Unlike the angular, blue-lit appearance of most Sentinels, Watchers have curving carapaces with orange lights. They have a number of appendages, including what appear to be legs hanging below the midsection and two large disks on both sides. Most of these segments lack physical joints and are held together by energy fields. Above the midsection there appears to be a head with stylized facial features.


Following the Human-Forerunner War and the discovery of the Flood, the Prometheans, under the leadership of the Didact, stood in opposition to the radical faction of Builders led by Master Builder Faber, who proposed the construction of the Halo Array. They lost the political battle and were subsequently removed from the Ecumene Council, with the Master Builder's allies rising to power in the Council instead. Disgraced, the Didact and some of the other highest-ranking Prometheans were allowed the dignified choice of exile in a Cryptum, while some of the lesser-ranked commanders were accorded more severe punishments.

After a thousand years of exile, the Didact was reawakened amidst the Forerunner-Flood war. Shortly after his revival, a radical shift occurred in the Council, and Faber lost his political power due to his crimes against the Mantle. Called upon to defend the ecumene against the onslaught of the Flood, the new Council elevated the Prometheans back to their former status, and the Didact resumed his duties as the supreme commander of Forerunner military forces. Under the Didact's leadership, the Prometheans would lead the ecumene's defenses against the Flood until the end of the conflict and the activation of the Halo Array. During the war, the Prometheans were primarily based in the fortified shield world Requiem. Requiem was sealed off under as of yet unknown circumstances toward the end of the Flood conflict; containing the Didact's Cryptum, as well as legions of mechanized Promethean forces, the shield world remained closed off for the next one hundred millennia.

Approximately five years after the end of the Human-Covenant War, John-117 and Cortana, drifting aboard the wreckage of the UNSC Forward Unto Dawn, came across the Forerunner world of Requiem, where they faced hostile mechanical Prometheans. During the events that followed, the Didact was awakened from his Cryptum.


The Composer was an ancient Forerunner machine capable of converting living beings into digital forms. The Composer was created by the Forerunners to save them from the Flood by allowing them to transcend biological forms altogether, granting them virtual immortality as digital intelligences. However, the Forerunners never perfectly mastered this capability and the resulting digital personalities became corrupted or fragmented and could no longer be restored to biological form. The Composer was also capable of slowing down Flood infection and the subsequent loss of individuality; however, this process was only temporary and still left the afflicted individuals in their deformed state. Physically, the Composer was an enormous, monolithic artifact engraved with patterns of lines characteristic of Forerunner architecture. The first known use of the Composer was when the Librarian employed its primary capability by extracting the memories of the surviving human warriors after the Charum Hakkor campaign in order to store their memory impressions in future generations of humans. The Lord of Admirals, supreme commander of all human forces and one of the humans to have their minds harvested, never saw the Composer directly and described its presence as "strange, ever-changing" and "multiformed", as it operated via intermediary Lifeworker machinery. As a result of the risks and irregularities involved with its usage, the Forerunners eventually abandoned the Composer and its existence was made a closely guarded secret known only to few. Even its actual nature remained obscure; whether it was a machine or being remained uncertain to most. Some even believed the Composer to be a "product of its own services"; a Forerunner, perhaps a Lifeworker, suspended in the final stages of Flood infection. Around 100,000 BCE, the Composer was used by the Master Builder to stave off Flood infection in certain Forerunners on Installation 07 to keep them in a docile state. After initial processing with the Composer, a form of harness prevented the infectees' decaying bodies from breaking down. While in control of Installation 07, Mendicant Bias and the Primordial also used the Composer to extract the ancestral memory imprints from Chakas and the other humans from Earth. Later during the Forerunner-Flood war, the Didact used the Composer to convert his Promethean warriors into robotic forms in order to allow them to combat the Flood more efficiently and without risk of infection. To bolster his numbers, the Didact used the Composer on a human population on Installation 07, turning them into additional forces in his mechanized army. The Composer later ended up in an asteroid field orbiting Installation 03. After the end of the Human-Covenant War, the United Nations Space Command Office of Naval Intelligence discovered the machine embedded in an asteroid and set up a research facility known as Ivanoff to study the artifact. Upon awakening on Requiem in 2557, the Didact immediately headed for the Composer and acquired it. Planning to use the device to neutralize all of mankind by forever imprisoning them into digital form, he first used it on the human personnel of Ivanoff; John-117 was the only survivor as a result of genetic modifications imbued by the Librarian. The Didact then set course for Earth in order to realize the final stage of his plan. The Didact successfully fired the Composer on an URNA metropolis, New Phoenix, but the effect was halted when John-117 destroyed the Didact's ship, and the Composer along with it, with a HAVOK tactical nuclear weapon.

Forerunner Particle Cannons are weapons used by the Forerunners during the Human-Promethean War. Forerunner Particle Cannons are enormous floating platforms used by the Forerunners as anti-air defences. Particle Cannons project a beam of energy similar to a Sentinel Beam to disintegrate any target in range. They are however vulnerable to ground based attacks and are structurally weak in the centre, as when a shot is fired into their primary weapon, the entire cannon is destroyed. A number of these weapons were encountered on Requiem in use by the Prometheans as anti-air defences, destroying a number of Pelicans and killing a number of Marines in the process. These cannons were destroyed by the Mammoth deployed to the surface by the UNSC Infinity, with the Master Chief providing targeting for the Mammoth. These cannons were controlled from a central core via an AI, before it was deactivated by Cortana.

Forerunner Beam Turrets are weapons used by the Prometheans during the Human-Promethean War. Forerunner Beam Turrets are turrets of a similar nature to those located on Shield 049, but smaller in scale. They are typically constructed by Watchers and possess a deadly, long range beam weapon, akin to a Sentinel Beam. When destroyed, Forerunner Beam Turrets disintegrate in a manner resembling that of Promethean Knights. A number of these turrets are hacked by Cortana on the Mantle's Approach during the Battle of Earth during which time they took on a blue light, like those of the Sentinels on Requiem.


Cryptums, or Warrior Keeps, were Forerunner objects created by the Prometheans. A Cryptum is a sealed capsule where a high-ranking Promethean would enter self-imposed exile as punishment for failure or dishonor. They are spherical in shape, with a dark gray outer casing broken by a pattern of angular, orange-glowing "cracks." When in use, their Forerunner occupants would enter a state of meditative hibernation known as "timeless xankara". During this time, the Forerunner would become unaware of the physical world around him, and could remain in a state of suspended animation for thousands of years. Cryptums required an extraordinary amount of force to breach once sealed. They denied access to every species except Forerunners. While the Cryptum preserved the consciousness of the Forerunner inside for an indefinite period, the Forerunner's physical body would still deteriorate, albeit at a significantly reduced rate. The body of the Forerunner would shrivel and lose most of its fluids, in a process similar to mummification. Once the Forerunner was removed from the Cryptum, the body would be placed in a restorative bath, and the body's supply of electrolytes, nutrients and other essential substances was thereby replenished. The body's muscle structure would then be regenerated, a process requiring several days. Although typically inert, when activated, a Cryptum is capable of powered flight and of scanning its surrounding environment. The nature of a Cryptum was unknown to most Forerunners, including Bornstellar Makes Eternal Lasting. However, he was aware that the violation of a Cryptum invoked dire consequences, one of which was angering the powerful Prometheans. A Cryptum was discovered in Djamonkin Crater by the young Forerunner Bornstellar Makes Eternal Lasting, containing the meditating Didact. Another Cryptum, also containing the Didact, was discovered over 100,000 years later by John-117 and the AI Cortana on the Forerunner Shield World Requiem. This Cryptum had not withered the user, as the Didact remained as physically fit as he had been when he entered. Additionally, it could double as a small ship, able to hover, travel through slipspace, and scan data from local objects. The Cryptum was able to travel at massive speeds, yet had no weapons and was vulnerable to UNSC ones such as MACs and missiles.

The Mantle's Approach was the Didact's personal flagship. This massive vessel was once captained by the Didact during the Forerunner-Flood War. Sealed inside Requiem along with its master by the Librarian, the Didact reactivated the ship after his awakening in July 2557. He jumped to Ivanoff Station alongside a Covenant remnant fleet, intent on reclaiming the Composer - an ancient Forerunner weapon with the power to wipe out entire species. The Didact test-fired the Composer on the station, then proceeded to Earth to settle his personal war with humanity once and for all. Unknownbest to him, John-117 survived the deadly pulse due to the Librarian's intervention. Pursuing the Mantle's Approach aboard a nuclear-armed F-41 Broadsword, the Spartan took out the ship's point defense turrets, allowing the UNSC Infinity to punch through the Mantle's hull with its MAC cannons. The Master Chief then fought his way through the ship, eventually finding the Didact controlling the Composer under an impenetrable force field. Cortana overloaded the shields by flooding the ship's mainframe with her rampant duplicates, allowing the Chief to confront and kill the Didact with a pulse grenade. With the Composer already firing upon New Phoenix, the Spartan manually detonated the HAVOK warhead as a desperate last resort. The Mantle's Approach was completely destroyed by the nuclear blast, taking the Composer along with it. The dying Cortana created a hard light barrier around the Chief at the very last moment, however, saving John's life at the cost of her own.

The Didact’s Ship served as the original transport for the Didact, Bornstellar Makes Eternal Lasting, and the humans Chakas and Riser. The ship was "grown" from a design seed planted under Djamonkin Crater by the Librarian. It was destroyed shortly after its activation, during the Battle of Janjur Qom. The ship was not "built" in the traditional sense, but rather "grown" from an object known as a design seed. The seed contained all the schematics and plans required to construct the ship, as well as the ship's slipspace flake, a piece of a much larger crystal used by the Forerunners in their slipspace drives. Most of the raw materials for the hull of the ship were apparently drawn from the central peak of Djamonkin Crater. The mountain was first dismantled and turned into several pillars arranged in a circle with an elevated platform in the centre. As the Didact, Bornstellar, Chakas and Riser stepped onto the central platform, the pillars began to spin rapidly, changing their shapes to form the hull of the ship. The vessel was highly advanced, even by Forerunner standards. It changed its overall configuration depending on the need; in space, the ship was an ovoid over 800 meters long.  When entering a planetary atmosphere, it took on a more aerodynamic shape, bowing out at the sides and growing massive landing pads as well as fluxor shields to protect against the blowback from atmospheric entry. Approximately one third of the ships mass was composed of fuel and engine reactants. The remaining space was used to accommodate personnel and could be configured at will, using various forms of hard light. It was stated as having enough space for 5,000 Warrior-Servants. Although newly constructed, the ship came fully equipped with a contingent of picket cruisers and an armoury stocked with spare combat skins, thousands of hand weapons and a host of other military devices, including the Didact's war sphinxes.

War Sphinxes were midsize Forerunner fighting suits used by the Prometheans. They were powerful war machines that were generally dropped from high orbit, and were capable of sweeping continents and decimating entire cities. The Didact's twelve war sphinxes, used by his warriors during the Human-Forerunner War, were left on Erde-Tyrene to guard his Cryptum. By the time Bornstellar Makes Eternal Lasting visited the planet in approximately 100,000 BCE, these suits were considered antiquated and outdated. More advanced versions of the war sphinx continued to be in use during the Forerunner-Flood war, alongside the more streamlined and less ornate Seekers used by Builder Security. The war sphinxes were described as being ten meters high and twenty meters long, with an elongated tail that provided lift and power. From the "tail" rose a large rounded torso with a command cabin perched on top. As was common with Promethean combat constructs, the command cabin was designed to resemble a Forerunner face, with features arranged in an angry or stern expression and two viewports serving as "eyes". They also had limbs, with joints of hard light. Much like Onyx Sentinels, two sphinxes could also merge to create a larger unit, which still retained a similar "face" at the forward surface. War sphinxes were programmed to contain samples of their wearer's mental patterns and personalities before they were killed in battle. These preserved personalities were less complete than Durances, but could still be studied by a commander to gain useful information. The Didact kept the final impressions of his children, who were killed in battle, within their war sphinxes.