Origins

150,000 BCE - The Forerunners rise as the preeminent species in the Milky Way Galaxy by advancing technological discoveries gathered from the remnants left by the Precursors. Believing themselves responsible for all those less advanced than they, the Forerunners initiate the Mantle, a galactic plan to stewardthe lesser races of the Galaxy.

100,300 BCE - The Flood Arrives from beyond the Milky Way, and begins to infect all Sentient life it encounters. The Forerunners create the Maginot Sphere, a defensive perimeter that protects their inner colonies from invaders. Hundreds of millions of Sentient creatures are assimiilated and despite opposition from the advanced armies of the Forerunners, the Flood thrives. The Forerunners realize the only way to eradicate the Flood is to destroy its food suply, i.e., sentient life. They create the Halo Array and the Ark as a means of saving selections of all the species of the Galaxy.

100,043 BCE - The Forerunner create Mendicant Bias, an exceptionally strong combat Ancilla that is built to battle the Flood Gravemind. Mendicant Bias is intended to lure the Gravemind out of the Maginot Sphere long enough for the biomass of the Flood to be destroyed. The Librarian, a female Forerunner responsible for saving sample species, comes upon an early Human species on Erde Tyrene, later known as Earth. The entire species is removed from the planet and moved to the Ark.

100,000 BCE - Mendicant Bias, corrupted by the Gravemind, becomes rampant and declares the Forerunners overindulgent and arrogant. It joins with the armies of the Flood and leads them against the Forerunners. Mendicant Bias survives aboard the Forerunner Dreadnought that later lands on the future San 'Shyuum homeworld. The Forerunner activate the Halo Array. All recorded sentient life in the Milky Way Galaxy is exterminated except the sampled species on the Ark. Once the Flood threat is ended, the sample species are reseeded across the Galaxy, including Humans on Earth, and they begin to repopulate their homeworlds. The remaining Forerunners leave the Orion Arm of the Milky Way Galaxy.



Between the 150,000 BCE and 100,000 BCE, the Human-Forerunner War takes place. Though the humans lost this war as well as their empire, they were one of the only civilizations reconized by the Forerunners to come close to their own technology.

During the Forerunner-Flood War, there were hundreds of attempts at eradicating the parasite, but none were successful. This led the Forerunners to the plan to eliminate all sentient life throughout the galaxy. Even after the firing of the rings, several samples of the Flood remained in containment on each of the 7 Halo Installtions, so that one day, the Moniters could find a cure to the Flood.