Conservation Measure
From Halopedia, the Halo wiki
The Library Project[1] was a massive undertaking to index and preserve biological diversity during the Forerunner-Flood War.
History
When the possibility that the only way to defeat the Flood would be to use the Halo Array, the Forerunners began an effort to take samples of life from the worlds they had found, including sentient lifeforms. These samples would then be taken to the Ark for preservation. There were a number of problems at first, mainly by categorizing the races into specific categories.[1]
As it became increasingly obvious that the Array would be the only means to defeat the emerging Gravemind, the Librarian, the head of the Library Project, urged her husband, the Didact, to fire the Array. But the Didact, still clinging to the Mantle and unwilling to kill his wife with the Array, constantly delayed activating the Array. In an effort to force the Didact's hand, and knowing that the Flood would soon find the Ark with Mendicant Bias' help, the Librarian destroyed her keyships on Earth, stranding her in the Array's radius of fire. Without any option left, the Didact fired the Array. [2]
After the Flood was defeated, automated systems on the Ark began the process of repopulating the galaxy, sending all the races back to their respective homeworlds. While a success, the Library Project also sent each race back to a Tier 7 scale, forcing the sentient races to start over.[1] Two races (the San 'Shyuum and Sangheili) would end up worshiping the Forerunners as gods, something the Forerunner hardly anticipated. And despite being no longer necessary, the data within archives were preserved at the Ark, a revelation which surprised 343 Guilty Spark[2]
