106,538 BCE

Circa 106,538 BCE,^{[note 1]} human colonists arriving at a ravaged planet on the edge of the Milky Way Galaxy discover an exceedingly ancient stasis capsule. This capsule is the prison of the ancient being known as the Primordial, supposedly the last intact Precursor. Yprin Yprikushma transports the capsule and its prisoner to Charum Hakkor for further study.^[1]

Yprikushma's science teams revive the Primordial and place it in a timelock held in a vast arena on Charum Hakkor, soon after devising a way to communicate with the creature. The answers given by the Primordial to the humans' questions about the Flood are so traumatizing they are believed by Forthencho to have demoralized humanity to the point of contributing to their defeat against the Forerunners later on.^[1]

Yprin Yprikushma begins to push humanity to conduct more intensive research into Forerunner technologies recovered during earlier human-Forerunner conflicts. Through the technological advances gained, she buys humanity several more decades in its war with the Forerunners.^[1]

Some time afterward, the Flood begins to recede from the galaxy; while this is thought to be due to a cure created by humanity, no cure ever actually existed; the Flood's withdrawal is instead due to the Gravemind's long-term strategy.^[2] With the Flood seemingly dying out, all traces of the parasite's existence are eventually removed from the Milky Way by humans, their San'Shyuum allies, and Forerunner Warrior-Servants.^[3] Throughout the war, most Forerunners remain unaware of the Flood's existence, believing stories of the parasite to be an excuse for humanity's aggressive expansion. The Flood will not be seen again for nine millennia.^[4]

Notes

^ Halo: Primordium specifies that the Primordial was discovered 40 years before "the last of the human-Forerunner wars". This is assumed to refer to the final 53-year conflict fought mainly in the Charum Hakkor system, as this is the longest mentioned continuous conflict which can be reasonably said to fall within the "few extra decades" Yprikushma bought humanity with her subsequent work.