BIRTH OF AN EMPIRE
Most of the history of the Forerunners is shrouded in mystery. What is known is the entire Forerunner species, like most species in the Milky Way, were created by the Precursors millions of years ago. When the Forerunners became too powerful and arrogant, the Precursors deemed them unfit to protect the Mantle, and decided to eradicate the galaxy of them to give ancient humanity their turn at earning the right to be defenders of the Mantle. When the Forerunners learned of this plan, they went to war, defeating and wiping out all Precursors from the Milky Way and Large Magellanic Cloud nearby, who were too shocked to fight back. This war shamed the Forerunners, who erased it from their history, not even allowing those who fought to return to Forerunner society. The Forerunners continued their dominance over the galaxy for the next ten-million years, growing and expanding their reach to include over three-million worlds within the galaxy.
Although the Precursors were wiped out by the Forerunners, their legacy lingered. Some Precursors avoided complete death by converting themselves into a desiccated powder and sending it via ships to the edges of the Milky Way. At least one other was mutated and locked away on an asteroid in the depths of space, biding their time until they were found.
Their time came when ancient humanity stumbled upon the powder, feeding it to their pets and through continued mutation, created the Flood. The threat the Flood posed to humanity forced them to expand their territory as worlds were lost, bringing them into contact with the Forerunners and sparking the Human-Forerunner Wars. Fighting both the Flood and the Forerunners was too much for them to manage, and it almost consumed them completely, until the discovery of the Primordial on a rock in deep space, who unbeknownst to humanity, took command of the Flood and sent all of them out of the galaxy. This nearly allowed humanity to survive against the Forerunner threat, but a betrayal by their allies the San’Shyuum tilted the war in the Forerunner’s favor permanently.
Having won the war against humanity, the Forerunners allowed some humans to survive, though they were devolved as punishment and to not pose a continued threat to the Forerunner empire. Meanwhile, the Didact, commander of the Forerunner military, tried using his hard-won political capital to support his plan for building hundreds of shield worlds across the galaxy, should the Flood return. He was successful for a while, but eventually the Master Builder convinced the Forerunner ecumene that his plan for building a intra-system defense platform known as the Halo Array, which was later redesigned to become a galactic weapon of last resort against the Flood. To avoid political retaliation on himself and all Warrior-Servants from the Master Builder and the entire Builder rate, the Didact placed himself into exile, spending the next thousand years isolated from the galaxy in a cryptum.
FIGHT FOR SURVIVAL
Inevitably, the Forerunner’s worst fear, that the Flood would return, came to pass. They rapidly began taking entire solar systems from the Forerunners, and within two-hundred years had made huge in-roads in the Milky Way. The Forerunner’s situation was made significantly worse when, during a test-firing of the Master Builder’s new Halo Array, the Primordial was released from his time-lock on Charum Hakkor, eventually convincing the Forerunner AI Mendicant Bias to fight for the Flood and commandeering one of the halo installations. Through the workings of the Librarian, the Didact was finally revived from his exile, though he would quickly be captured by the Master Builder and left for dead.
The Master Builder’s actions with the Didact and during his ruthless attack on Janjur Qom finally crossed a line with the Forerunner government, however, and with the threat of the Flood more immediate than ever, the Master Builder was put on trial on Maethrillian for his crimes against the Mantle. This trial barely had a chance to get started, though, as Mendicant Bias, along with the Primordial and the stolen halo, arrived at Maethrillian, sparking a violent battle that left the entire Forerunner capital devastated.
Pushed back onto their heels, the remaining Forerunners fought valiantly against the Flood, spending the next several years trying to keep the Flood from making further advances into Forerunner territory, but to no avail. Eventually the Forerunners lost the entire galaxy, with the remaining forces all converging at the Greater Ark, where they made a heroic last stand, though even with one large fleet and a halo remaining, the Forerunner forces were quickly overrun and the Greater Ark was destroyed. Only a select few managed to escape the battle before becoming completely overwhelmed, running to the Lesser Ark, the forge for the Neoteric Halo Array and galaxy-spanning weapon of last resort. Here, the IsoDidact initiated the Great Purification, eliminating all sentient life from the entire Milky Way and clearing out all traces of the Flood from the galaxy.