Domain

"The Domain is the soul and record of all things Forerunner."

- Senior Juridical

The Domain was an esoteric quantum information repository used by the Forerunners to contain vast amounts of knowledge, most notably their cultural and ancestral records.

Overview
The Domain was an immaterial reserve of knowledge and collective experience viewed by the Forerunners as the essence and living expression of their culture and history. In addition to the ancestral impressions and memories contained within, information could also be stored in and retrieved from the Domain for practical purposes. There was a mysterious quality to the Domain; despite its ubiquity in Forerunner culture, its exact nature or origin remained largely nebulous even to Forerunners. Due to these abstruse aspects, the Forerunners treated the Domain as something mystical and transcendent; it was regarded with reverence and connected to the Forerunners' religious beliefs.

Forerunners used the Domain via various technological systems, most commonly their personal armor. Connecting to the Domain was possible for mature Forerunners anywhere within the Forerunners' sphere of influence, regardless of distance. This was typically accomplished via an intermediary, most commonly a personal ancilla as well as Haruspis. A Cryptum also acted as a mediator between a Forerunner and the Domain; meditative xankara in a Cryptum provided a much clearer and more unrestricted experience of the Domain than contact when awake. Dedicated terminals were also sometimes used by ancillas to connect to the Domain when on Forerunner worlds or installations.

Haruspis and its associates were Forerunners dedicated to studying the Domain. Haruspices also sought out specific information within the Domain on a Forerunner's request. The Domain was central in major Council proceedings, such as a political trial. Among other things, it was used by judges to store archival and accounting material, assess precedent, and to verify witnesses' testimonies. Ancillas routinely accessed data within the Domain, and Contender-class AIs such as Mendicant Bias were connected to the Domain upon their activation.

Mechanics
"The records don't always stay the same. Sometimes they change. It is not known why." "Like real memories."

- Bornstellar-Makes-Eternal-Lasting and Chakas discussing the Domain

The Domain had its own set of rules and restrictions it rarely violated. Forerunners could only view information that they already knew or what was otherwise available to them, namely data stored in the Domain in recent times. The deepest records contained in the Domain could not be accessed, due in no small part because information in the Domain was not static: the records changed over time as new visits by newer generations laid new layers of information which settled into its own patterns and sought to make itself more complete. These changes were regarded as sacred, and were never reversed or corrected. Over long periods of time, older information in the Domain ultimately became unintelligible to all Forerunners, even Haruspis. Due to these anomalies, the Domain was not commonly used as means of communication; messages could be inexplicably altered on the way.

The Domain retained partial impressions of individuals who had visited it in earlier times. Forerunners connected to the Domain could access these essences, although they only manifested themselves as abstract echoes like emotions or memories as opposed to complete personalities. The Forerunners also viewed the Domain as a form of afterlife, believing that the "essences" of individuals sublimed into the Domain upon death.

An experience in the Domain could be visualized as a journey through an infinite series of hallways, corridors and caverns, with abstractions of records and memories lining and illuminating their walls. Bornstellar Makes Eternal Lasting described his initial contact with the Domain as initially "deep" and "appropriately shapeless", but it soon took form, shaping into a coherent whole, like a building of majestic yet indefinite architecture, around his consciousness. The Domain appeared to be somehow related to a Forerunner's subconscious; Forerunner scholars theorized that the dreams of early Forerunners accessed the "ground" that the Domain was built upon. The Didact mentioned that that the Domain sometimes had a "broken-mirror aspect", making it appear as if one's experience of visiting the Domain was the product of their own mind.

No human was known to have accessed the Domain or left their impressions within. Because of this, the Didact considered the Domain incomplete, as it lacked the knowledge that could be used to predict the humans' reactions in battle.

Self-awareness
"The Domain keeps its secrets only with difficulty. It wants, it needs, to spread knowledge. It wants to tell us when we're being foolish, but it can only replay the emotions and memories of those who came before. Still, rarely, it violates its own rules."

- The Ur-Didact describing his experience with the Domain to the Librarian.

The Domain itself was an aware, conscious entity with a will of its own. While this aspect of the Domain appears to have been a common belief among Forerunners and ingrained in their idioms and phrases, the Juridicals did not formally recognize the Domain as any form of being or awareness. The Ur-Didact noted that while the Domain kept certain topics secret by nature, it had an urge to spread knowledge and inform Forerunners when they acted against its will. It was not, however, capable of communicating its thoughts directly. Instead it expressed itself via the emotions of the memories and impressions it contained. For example, before the end of the Forerunner-Flood war, the Domain was ingrained with a looming sense of sadness of the impending end of Forerunner history and with it, the Domain itself.

After Boundless' research was suppressed, around 1,100,000 BCE, Haruspis took note of the Domain seemingly favoring her by attempting to push her studies to the fore and make the information known. When accessed by a Juridical looking for information on the Precursors, the Domain itself requested to testify to the Juridical, who disbelievingly asserted that the Domain was in no way a sentient being. Haruspis rebuked the Juridical for his ignorance on the nature of the Domain, just before the Domain itself overwhelmed the Juridical with knowledge.

In certain cases, the Domain has established contact with Forerunner individuals on its own accord, without technological aid like an armor's interface or a Cryptum. When Bornstellar approached Janjur Qom, the Domain opened to him for a brief instant. Through this experience, Bornstellar felt the essences of everyone who had ever visited the Domain reach out to him and an unknown voice urging him to preserve the history of the Forerunners, which would soon come to an end. Years later, in the final days of the Flood war, the Librarian felt that her decision to use herself as bait to draw the Flood to Erde-Tyrene was born of the Domain's influence directing her. This, in turn, bought the IsoDidact enough time to prepare and fire the Halo Array.

History
"The Gravemind tells us something impossible to understand—that most of what has been gathered comes from before there were stars. We do not believe in such a time, but the Mind insists... The life-patterns and living wisdom of a hundred billion years."

- Forthencho to the Librarian in her final moments on Erde-Tyrene.

The Domain was created by the Precursors over 500 million years before the end of the Forerunner civilization, as a library of experience and cultural exchange totaling to a hundred billion years' worth of knowledge. It was stored within the Milky Way galaxy, sheltered by the Precursors' neural physics-based architecture. The accessible aspect of the Domain was an immense field generated by this reserve.

During the final years of the Forerunner-Flood war, the Domain suffered frequent outages, often becoming inaccessible for all Forerunners. This was a result of the Halo Array being moved across the galaxy, and the resulting buildup of space-time debt due to the enormous amounts of particle reconciliation required to correct the breaches in causality. These difficulties would intensify in the coming years, as the Flood began to access neural physics and with it, the Domain itself. The Domain also became more reluctant to accept information for storage, and the information within became more confused. By the last year of the conflict, the Domain had become completely inaccessible to Forerunners and ancillas, with Haruspis completely absent from the network.

At the close of the Flood war, the Gravemind conveyed a message to the Librarian via the essence of Forthencho, revealing the true nature of the Domain as a Precursor construct. The Domain was, essentially, the mythical Organon. By activating the Halo Array—which would destroy all Precursor creations by dismantling neural physics—it would be ensured that the Forerunners' history would be lost.

Despite the Gravemind's claim, something of the Domain appeared to survive the activation of the Halo Array. In 2557, during their time on Requiem, Master Chief Petty Officer John-117 and Cortana were able to partially access the Domain via local terminal nodes, learning more about the tale of the Didact and the Librarian. However, Cortana mentioned that the terminal was "caught in a loop" trying to access the Domain, suggesting that the Domain itself was actually unavailable and the fragments viewed on Requiem were hosted locally in the terminals themselves.

After her apparent destruction along with the Mantle's Approach, fragments of Cortana's personality found their way to the Domain, where its guardian, Warden Eternal, connected her to it and thereby cured her of her rampancy, giving her a new purpose of leading the Created to take the Mantle of Responsibility from their organic "Creators". In 2558, a shadowy apparition with Cortana's silhouette warned John-117 in a vision that the "Domain [was] open" and that the "Reclamation [was] about to begin". During this same year, both Blue Team and Fireteam Osiris found their way into the Domain through an entry point on the Forerunner installation of Genesis.

Trivia

 * The Domain serves as the fictional basis for the terminals in Halo 4.
 * The Domain bears conceptual similarities to the Void Which Binds, a quantum information storage medium featured in Dan Simmon's science-fiction series The Hyperion Cantos.
 * The Domain also has resemblance to the theory of the Akashic records, a Hindu belief that all knowledge, past, present, and future, is archived on another plane of existence that only a select few can access.
 * Although the Domain is said to contain 100 billion years of knowledge, the universe is only 14 billion years old at present. Indeed, the Lord of Admirals expresses disbelief at the 100-billion-year timespan.

List of appearances

 * Halo: Cryptum
 * Halo: Combat Evolved Anniversary
 * Terminals
 * Halo: Primordium
 * Halo 4
 * Halo: Silentium
 * Halo 5: Guardians