![halo wars play as flood halo wars play as flood](https://media.flixfacts.com/inpage/ecb_build/live/microsoft/1180067_43_files/658/assets/2986_Xbox_HaloWars2AtN_8.png)
Almost every time the Flood have made an appearance, they have been a massive threat that overshadows everyone else. They've also made sporadic appearances in short stories and novels in the Halo Expanded Universe. In the games themselves, the Flood have made appearances in Halo: Combat Evolved, Halo 2, Halo 3, both Halo Wars titles. Related: Halo's Master Chief Should Join Super Smash Bros. This knowledge lets them use weapons, fly spaceships, and even intellectually corrupt Artificial Intelligence to serve the Flood's ends in a form of corruption called the 'Logic Plague.' The Forerunners were overrun by this and much more, and the UNSC and Covenant had to learn this the hard way when the Flood appeared to them. Once enough are infected, the outbreak reaches a critical mass and forms a Gravemind, which contains the accumulated knowledge of the Precursors and everyone they've ever infected.
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What makes the Flood such a dangerous threat is the fact that they retain the intelligence and knowledge of every living being they infect. But the Forerunners also kept Flood samples imprisoned on the Halo Rings and in other facilities across the galaxy, which would lead to the UNSC and Covenant encountering them in the 2500s. This included humanity and all the species that made up the Covenant while leaving behind countless ruins of their technology. Of course, the Forerunners had saved as many species as they could, bringing them to the Ark and reseeding them all over the galaxy after the Forerunner-Flood War had ended. Related: How Halo 2 Redefined Multiplayer Gaming This ultimately forced the Forerunners to create the Halo rings and unleash them upon the galaxy, wiping out the Flood, Precursor structures and countless other life forms across the galaxy. They simultaneously did everything to shatter the Forerunner's own beliefs, revealing that there was no cure and that the Forerunners themselves had stolen the Mantle from humanity, as opposed to the Precursors choosing them as the modern Forerunners believed. Several millennia later, the Flood returned and attacked the Forerunners with a vengeful ferocity for what the Forerunners had done to them as the Precursors millions of years ago.
HALO WARS PLAY AS FLOOD SERIES
This led to a series of events that included the Flood retreating, fooling both humans and the Forerunners into thinking a cure had been found, the subsequent devolution of ancient humanity into a more primitive state, and Forerunner political gambles while hoping to find out what the cure was. The humans fought a war against the Flood, the collateral damage of which drew the attention of the Forerunners, and caused them to fight the humans after the humans started glassing infected Forerunner worlds to stop the spread. But this powder mutated over millions of years, and eventually became the Flood, as the Ancient Humans found out the hard way. Some Precursors survived the massacre and reduced their physical forms into powder to be restored later. They rose against the Precursors, who were so amazed at the violent capabilities of their creations that they didn't even try to fight back, which led to the events of the Forerunners taking control of the Mantle and the galaxy.
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The Forerunners didn't take this too kindly. The Precursors ultimately chose humankind for the Mantle, a philosophy dictating that the greatest species should care for and nurture all the rest. They also seeded the galaxy with countless forms of life, two of their greatest creations being the Forerunners and humanity.