97,445 BCE

In approximately 100,000 BCE, the Forerunner-Flood war came to a close with the activation of the Halo Array. It should be noted that all of the events listed here are approximate at best, occurring over the course of several years during the last decade before the firing of the Halo rings around the year 100,000 BCE. As no definite chronology has been established for that timeframe, the events therein are recorded here for the sake of convenience.


 * The Librarian visits the primary San 'Shyuum quarantine world Janjur Qom to collect specimens of the San 'Shyuum as part of the Conservation Measure, sparking unrest among the San 'Shyuum population. After Master Builder Faber arrives some time afterward to question the San 'Shyuum elders about the Flood, the San' Shyuum rebel against his forces.


 * The Ur-Didact is resuscitated from his exile in a Cryptum by Bornstellar Makes Eternal Lasting, Chakas and Riser. They later make their way to Janjur Qom, where they are captured by Master Builder Faber. The Didact is interrogated and left to die in a Flood-infested system, while an offshoot of his consciousness lives on in Bornstellar's body through an imprint acquired in his mutation.


 * Shortly afterward, the Master Builder orders the Contender-class ancilla 05-032 Mendicant Bias to use Installation 07 to put down the San 'Shyuum rebellion by sterilizing the entire system.


 * As a result of the Master Builder's activation of the Halo ring, many Lifeworkers and Warrior-Servants on Installation 07 rebel against his forces, but are mostly defeated.


 * A crisis occurs in the Ecumene Council due to the Master Builder's unauthorized activation of Installation 07; many councilors resign in protest while younger ones take their place. Faber is arrested and placed on trial in the Forerunner Capital. Eleven of the Halos are brought to the Capital, awaiting a decision to have them decommissioned. Installation 07 and Mendicant Bias remain missing.


 * During Faber's tribunal, Mendicant Bias, convinced to turn against its masters by the Primordial, brings Installation 07 to the Capital system and launches an assault on the Forerunner government. While the Council's fleets respond to the attack and several of the Halos are destroyed, Mendicant successfully fires Installation 07 before the Halo is forced to retreat into a system near the galaxy's edges.


 * Having survived Mendicant Bias' attack on the capital, Bornstellar, Glory of a Far Dawn and Splendid Dust of Ancient Suns arrive at the greater Ark, where they are healed by the Lifeworkers. As most Forerunners believe the original Didact to be dead, the Didact's consciousness takes control of Bornstellar in order to assume command of Forerunner military forces after a thousand years of exile and continue his mission against the Flood; subsequently, Bornstellar adopts the title IsoDidact.


 * Shortly afterward, the IsoDidact and his fleet track down Installation 07. Although the Halo takes heavy damage, it survives and is transported to the greater Ark. Afterwards, the installation is sent to its final location, to be later joined by the six rings of the newer Halo Array.
 * The Primordial is imprisoned once again, and is interrogated - and eventually executed - by the IsoDidact.
 * Mendicant Bias is captured, deactivated and disassembled to its disparate components which are then distributed across the ecumene.
 * The mind of a mortally wounded Chakas is used as the template for the monitor later to be known as 343 Guilty Spark.


 * The Ecumene Council is reconstituted and the Didact's plans of a strategy to use shield worlds to combat the Flood are taken into serious consideration again. The use of the Halos is delayed.


 * The Juridical rate is given unrestricted access to all citizens of the ecumene by the Council, with the mandate to investigate matters surrounding the attack on the Capital, Forerunner and human origins, as well as the fate of the Precursors. To this end, the Juridicals dispatch Catalog to collect testimony from key Forerunner figures, including the Librarian, Ur-Didact, IsoDidact and Faber.


 * The Librarian and the IsoDidact arrive at Earth to oversee its evacuation operation and to give their testimonies to Catalog. However, the Flood's arrival in the sector prompts the IsoDidact to leave to defend the core of the ecumene while the Librarian continues her mission; the two will not reunite until four years later.


 * 05-032 Mendicant Bias is reassembled and reactivated by a Gravemind after the Flood overruns the facilities in which the components of the AI were held.


 * The Ur-Didact, having been left to die by the Master Builder, encounters active Precursor star roads near Uthera Midgeerrd. The Didact is subsequently captured and corrupted by the Gravemind. Afterwards, the Gravemind releases the Didact, who is rescued and taken to the Capital system by the Master Builder.


 * The Flood begins to reactivate and appropriate formerly dormant Precursor artifacts, allowing them to easily overpower Forerunners in combat. Already weakened and exhausted Forerunner defenses continue to fail at an increasing rate.


 * After the Capital system is lost to the Flood, command of the ecumene and the bulk of its remaining population is placed at the greater Ark. In the face of imminent defeat, a decision is made to use the Halo Array to purge the galaxy of life and thus starve the Flood. The IsoDidact is tasked with carrying out this plan.


 * Mendicant Bias and its fleet of Flood-controlled ships and Precursor constructs assault the greater Ark.


 * While the Forerunners attempt to evacuate the greater Ark, the Ur-Didact uses the Composer to harvest the preserved human specimens on the nearby Omega Halo in order to use their patterns to create AIs for his army of Promethean Knights, a desperate and futile effort to combat the Flood via conventional means.


 * Master Builder Faber fires Omega Halo, sterilizing the local galaxy of Path Kethona of sentient life and clearing a temporary path past the star roads laying siege on the greater Ark.


 * The greater Ark and Omega Halo are destroyed by star roads; Faber and most high-ranking Forerunner commanders are killed on Omega Halo, while the IsoDidact is saved by Monitor Chakas. Only a fraction of the Lifeworkers' biological specimens survive and are transported to the secret Installation 00 by the few surviving Forerunners.


 * The Librarian, horrified by the Ur-Didact's genocide of the human population of Omega Halo, sends Chant-to-Green to collect more humans from Earth to ensure their numbers will be sufficient to repopulate the species. The Librarian herself infiltrates Requiem and imprisons the Didact in a Cryptum.


 * The Librarian journeys to Earth, planning to draw the Flood there in order to give the IsoDidact time to fire the Halo rings. She sends Chant-to-Green to the lesser Ark, along with the remaining humans gathered from the planet, and passes her title of Lifeshaper on to Chant.


 * At Installation 00, the IsoDidact assigns the monitors for each Halo installation and has the rings distributed across the galaxy.
 * 343 Guilty Spark is assigned as the caretaker of Installation 04.


 * The Librarian, stranded on Earth, initiates the burial process of the Portal at Voi. As she spends her last hours in the savanna, the Gravemind sends down imprinted ancient human essences to reveal the Domain's true nature as a Precursor creation; as a result, the Domain will be destroyed when the Halos fire, leading to the loss of not only all Forerunner history but also the knowledge the Precursors had collected over the course of billions of years.


 * As the IsoDidact prepares to activate the rings, Mendicant Bias assembles all Flood-controlled vessels into a fleet of 4.8 million ships, and breaches the Maginot Sphere. On the other side awaits Offensive Bias with the remains of the Forerunner fleet. As the two fleets engage each other in an enormous naval battle, the Halo Array is fired. The Halo pulse kills all sentient life within three radii of the galactic center, including any Forerunners not located on the Ark or within Shield Worlds. Minutes after the firing of the Array, Mendicant Bias's fleet is decimated by Offensive Bias.


 * The remains of Mendicant Bias are brought to Installation 00. The surviving Forerunners hold a trial to the AI for its betrayal; Mendicant Bias is entombed in the installation afterward.


 * Every sentient species indexed in the Ark is returned to their homeworlds as a part of the Conservation Measure, the Homo sapiens species begins migrating out of Africa.


 * The few surviving Forerunners go into self-imposed exile.