Isu

## Physical characteristics

### Height

**Natural:** 5 ft (1.5 m) to 7 ft (2.1 m)**Modified:** 7 ft (2.1 m) to 8 ft (2.4 m)

### Mass

**Natural:** 100 lbs (45 kg) to 250 lbs (113 kg)**Modified:** 350 lbs (158 kg) to 450 lbs (204 kg)

### Lifespan

**Natural:** 250 to 300 years**Modified:** Indefinite

## Sociocultural characteristics

### Notable members

* Forthencho
* Yprin Yrpikushma
* Chakas
* Jupiter
* Juno
* Minerva

The **Isu** (*Homo sapiens divinus*) are an extinct mammalian human species which evolved on the planet Earth, and are the designers of the modern human species (*Homo sapiens sapiens*).

## History

### Origin and rise

Having evolved from hominid primates on Earth, the Isu split off from the Pak and the other human species after their common ancestors began to spread out of Africa. The Isu's earliest known spacefaring occurred around 1,100,000 BCE, when they settled on numerous worlds along the galactic margin; these regions would be targeted by the Flood's initial assault over a million years later. Early in their history, long before encountering the Forerunners, the Isu and the other human species in the galaxy underwent a series of technological dark ages, which left their populations scattered across many worlds and resulted in the loss of most of their records, including the knowledge of Earth being their original homeworld. It was not until much later when scientists led by Yprin Yprikushma confirmed that the Isu had indeed arisen on Earth. During this initial era of expansion the Isu interacted with a multitude of alien species, but developed a fierce rivalry with the Forerunners, their only technological superiors. Around 150,000 BCE the Isu moved their civilization outward along the Orion Arm, possibly to flee Forerunner control.

After recovering from their dark ages, the Isu made the former Precursor world Charum Hakkor their capital, to be close to one of the greatest collections of Precursor structures. Humanity also formed an alliance with the San'Shyuum species in order to gain access to their advanced technology. At their height, humanity's technological advancement, combined with their understanding of Precursor technology, nearly rivaled that of the Forerunners.

### Thousand Year War

This civilization encountered the Flood in approximately 107,445 BCE and went to war against the parasite after discovering its true nature. After losing many planets to the Flood the Isu desperately invaded a minor sector of the Forerunners' Ecumene, though, in at least some instances, they were actually sterilizing Flood-infected Forerunner worlds. The Forerunners responded violently to this aggression and waged war with the humans and their San'Shyuum allies. The resulting conflicts lasted for a thousand years.

Forty years before the last conflict between the Isu and the Forerunners, a human expeditionary group encountered an ancient being held in hibernation on a planet near the galaxy's edges. Under Morale Commander Yprin Yprikushma's orders, this being, known as the Primordial, was placed in a stasis capsule and transported to Charum Hakkor for study. Isu researchers found a way to communicate with the entity, asking in vain for answers to various scientific or metaphysical questions, receiving no useful responses. Instead, the being revealed disconcerting truths about the Isu's origins, and their future; this was believed by some to have caused the demoralization of Isu culture and thus contributed to their defeat against the Forerunners. The scientists also inquired the Primordial about the Flood; the answers they received were so traumatizing that many present there committed suicide.

After a certain point, the Flood's rampage throughout human territory stopped. The Flood no longer infected humans and instead began to rapidly die out, with both humans and Forerunners sterilizing the remaining infestations. Based on this pattern, the Forerunners came to the conclusion that humanity had discovered a cure for the Flood: according to Forerunner records, the Isu sacrificed a third of their total population, implanting them with destructive, artificially programmed genes used to target the Flood on a genetic level. In reality, however, the Flood had receded by its own volition after the sacrifice; no truly functioning cure was ever created or used by the Isu, though both Forerunners and the Isu themselves remained under such an illusion.

Stretched thin due to fighting two wars at once, the humans were finally driven to their capital of Charum Hakkor. After holding off for fifty-three years they were defeated at the hands of the Forerunners, led by the Didact. Before the fall of Charum Hakkor some humans suggested they should draw out the Flood and use it against the Forerunners. However, this strategy was denied, as the human leadership chose to face defeat rather than allowing the Flood to spread.

### Downfall

As punishment for defying the Forerunners, nearly all of the Isu, and their close genetic relatives were wiped from the galaxy and the remnants and technological achievements of their civilization were extirpated. Furthermore, the surviving Isu were subjected to a process of biological devolution; live Isu were forced to consciously experience an artificially induced reversion of their evolutionary process, to the point of their bodies transforming to their ancestral forms and eventually losing intelligence. The remnants of the human genus were exiled to Earth, where they were overseen by the Librarian; while many Forerunners wanted to see the Isu exterminated, the Librarian had always been considered their greatest protector. In only a thousand years, humanity recovered many of their prior forms, along with many new ones, due to the assistance of the Librarian and her *geas*, as well as unknown factors not even the Librarian and her Lifeworkers could explain. Over twenty human species made recovery and formed separate populations on Earth, including the Isu, the Neanderthals, the b'asha*manush*, and the Florians. This meddling was noted to have considerably distorted Earth's natural fossil records.

The Forerunner victory proved disastrous for the galaxy, as the Isu destroyed all their research data and physical evidence concerning the Flood, including their supposed cure, as a last act of revenge to leave the Forerunners unprepared to face the incoming threat that led to the eventual firing of the Halo Array. The last Isu survivors on Charum Hakkor were subjected to thorough analysis and experimentation in order to discover their supposed Flood immunity; eventually, their patterns were extracted by Composers and archived in machine storage, where the Isu essences would be incessantly scoured for a cure for thousands of years.

The Librarian and Didact later learned that humanity had never developed a cure or a way to fend off the Flood. As the remnant of the Precursors, the Flood sought to punish the Forerunners for destroying them, and desired the continued existence of the members of the human genus for some unknown purpose. When the Forerunners retaliated against the Isu for invading Forerunner worlds, the Flood predicted that the Forerunners would try to exterminate the Isu. Of its own volition, the Flood abruptly receded from Isu territory, knowing that the Isu would temporarily rebound and thus unknowingly deceive the Forerunners into thinking they may have developed a cure. This caused the Forerunners to restrain themselves from eradicating the Isu completely and preserve a regressed remnant population, since they needed living Isu to study if their apparent Flood cure was to be found.

### Recovery

Forced to start again, the collective human genus tried in vain to reattain their former glory. Some human communities, such as the civilization built around Erde-Tyrene's largest city, Marontik, established wooden cities and steam-powered waterborne vessels nearly nine thousand years after the Thousand Year War. Most humans, however, lived in Tier 7 tribal communities, such as the one that was encountered by the Forerunners during the construction of the portal to the Ark in eastern Africa.

After the activation of the Halo Array, the Isu civilization regressed once again, and would remain Tier 7 hunter-gatherers for several millennia. As time went on, however, the Isu rose to dominance among the many species of humans left to redevelop in the post-Array era. Rediscovering many of the long-lost secrets that the Forerunners and their own ancestors had left behind on the world, the Isu developed into an extremely advanced Tier 4 civilization. In less than 20,000 years, they were already participating in low-end terraforming and stellar engineering. They possessed a talent for ecological manipulation, atomic power, and genetics. However, their populations refused to grow at a pace on par with their technology, and the power of quick and efficient space traveled also remained lost on them.

### Creation of humanity

Modifying their own genome to enable near-infinite lifespans, the Isu grew in their physical knowledge, but became cruel and decadent. They created the artifacts known as the Pieces of Eden, as well as a new species of human designated *Homo sapiens*, as a domestic work force to maintain their civilization. *Homo sapiens* themselves were derived from the Isu's own genome, which would lead to unforeseen consequences in the future. The genetic alterations made to the new human species were meant to make them more docile to the controlling power of the Pieces of Eden. However, apart from these manipulations, the new humans remained very similar to the Isu, the only differences being the height and the size of the skull. The two species were even capable of interbreeding. With early humans unable to comprehend the Isu for what they truly were, they came to be revered as deities.

### Uprising and catastrophe

Having been instigated by the theft of an Apple of Eden by the human Adam and the half-Isu Eve, the human rebellion soon erupted into a full-scale war with the Isu. While the Isu were more technologically advanced and powerful, it was humanity who had the advantage of numbers. The conflict lasted for a decade before abruptly ending when a coronal mass ejection, later to be known as the Toba Catastrophe, occurred, showering the Sol system in deadly radiation. The casualties on both sides were far greater than the Isu would have ever anticipated. The distraction of war had blinded them to all else, and their preoccupation with the conflict prevented them from seeing the signs of an impending danger from the heavens until it was too late.

Several Isu scientists not devoted to the war were aware of the imminent catastrophe and endeavored to prevent it by thinking up various ways to protect the Earth. The Capitoline Triad – consisting of Minerva, Juno, and Jupiter – decided to lock themselves away in the Grand Temple for years, only to test out a variety potential solutions, following which they experimented with the most promising results in underground temples called Flare Vaults spread across the globe. Despite this, all offered prospects failed miserably, with none providing adequate protection against the massive solar flare that was due to collide with the planet.

During this time, it turns out that Juno had made her own agenda for the world. Rather than save it, she planned to rule over the remnants after the catastrophe instead. As a result, she was subsequently imprisoned by Minerva and Jupiter. With their time having grown short, Minerva managed to construct a pedestal called the Eye, which created a geas in humanity's genetic memory in the hope that they would find these messages, and save the world from the catastrophe's reoccurence.

However, before she could use the device, Minerva had discovered that Juno had tampered with the Eye in a manner wherein she would be freed from her imprisonment upon it being activated. Having refused to release Juno from her prison, Minerva made the decision to destroy the device instead, thus condemning the world to face a second solar flare, which would flip the Earth's weakening magnetic field and reverse the polarity, making the planet geologically unstable.

### Later history

While both races survived the catastrophe, few of either species remained. Working together, they rebuilt their world, though humanity continued to view their counterparts as gods. Despite their survival, the Isu were unable to fully recover their numbers, and began an inevitable decline toward extinction.

They knew, however, that the catastrophe which had burned their world before would eventually repeat itself, and so they took steps to prevent it. Utilizing a second Eye she had built, Minerva recorded a number of holographic, yet interactive, messages to serve as a warning to those who entered the Vault under what would become the city of Rome. In it, Minerva warned of the impending doom, and spoke of the "temples" that could save Earth from destruction, built by those who "knew to turn away from war". Concurrently, several other members of the Isu took independent steps to influence the thriving human race, attempting to put their knowledge to stone or parchment, though these did not withstand the test of time. Barely a hundred years after the creation of the Temples, the Isu, and all other members of the human genus were extinct, leaving *Homo sapiens* the sole Reclaimers of the Milky Way galaxy.

## Biology

Alongside the other contemporary human species, the Isu were bipedal humanoid primates with four limbs, two arms and two legs. Isu had five fingers on each hand, including an opposable thumb, and five toes on each foot. Like the other human species, Isu possessed proportionally large brains for their size, and made frequent use of tools to enhance their abilities. They had a single heart and stomach, and bled red blood. Most, if not all, of these physical traits were passed on to their genetic descendants, the modern human species (*Homo sapiens sapiens*). Functionally, the only differences were the latter's truncated lifespan and improved docility towards certain Isu technologies, such as the Pieces of Eden.

Naturally, members of the Isu were not much larger, stronger, or intelligent than modern humans. After achieving Tier 1 status, however, the Isu gradually employed a wide array of genetic enhancement technologies which altered their DNA at a cellular level. These modifications resulted in a species which was possessed great strength and stature, as well as increased intelligence and a much longer lifespan. During the height of the Isu Empire, advanced medical technology allowed them to live practically indefinitely.

Genetically modified Isu had a triple-helix DNA structure and six primary senses: the normal five which humans had, as well as a sixth sense, sometimes called Eagle Vision. Eagle Vision allowed an individual to more accurately observe the people and environment around them, analyze and respond to threats before they arrived, and slow down or speed up their subjective perception of time.

While the Isu exhibited a range of morphological variation, they were overall remarkably similar in appearance to modern humans. They possessed straight to wavy hair textures, thin to full lips, and an overall similar facial composition to their modern counterparts. During the era of the Isu Empire, most of them had black or dark brown skin. However, following the firing of the Halo Array, and the species' subsequent relocation on Earth, lighter skin tones appeared among northern populations. In antiquity, the Isu interbred with nearly all of the other human species which inhabited Earth around their same time period, including Neanderthals, Florians, Denisovans, and Pak. Children of such unions often physically resembled one side of their ancestry more than the other, but were readily accepted by Isu society at large.

## Society

Isu believed themselves and the other human species to be the collective inheritors of the Mantle of Responsibility, a notion the Forerunners considered heretical. Ironically, the Precursors had actually intended for humans to inherit the Mantle instead of the Forerunners. The Isu believed in "creating many souls", and in expanding their population by conquering and claiming other worlds for their own. Within the Isu Empire,a polytheistic spirituality called Juhnen Paaw was practiced by Isu and other humans, which incorporated the worship of inanimate objects. Precursor artifacts were held higher than all others, and were frequently worshiped and studied, but never destroyed. Another Isu religion from this time period was the Daowa-maadthu, which taught about the roll and tug of the universe and its relationship to the individual.

Isu society during the Isu Empire was xenophilic and diverse, blended and mixed with the multitude of other human cultures which made up the empire. Scientific and technological fields were valued highest, but nearly all vocations maintained a spiritual aspect to their practice. True atheism was exceedingly rare among humans at the time. Though a majority of the Isu population was mixed, resulting from countless generations of interbreeding with the other humans, the highest political and religious offices were usually reserved for individuals with full Isu ancestry.

After the Thousand Year War and the centuries of constant warfare against the Flood, Isu society had become exceedingly militarized; officers wielded significant decision-making power, some military offices (namely that of the Political and Morale Commander) doubling as leadership. During the siege of Charum Hakkor, even Isu children were organized into their own defensive guards. Isu, along with their San'Shyuum allies, favored the domesticated Pheru, originating from the planet Faun Hakkor, as pets. The Pheru eventually became the first vectors for the Flood. Officers of the Isu fleets sported various kinds of white facial markings and typically had long hair. Warship crew members wore unadorned, form-fitting suits of powered armor, lacking any markings or other features denoting rank. For ceremonial occasions, more elaborate uniforms existed.