2. The Flood are fictional parasiticalien life forms in Bungie'sHalo video game series. They are introduced in Halo: Combat Evolved as a second enemy faction alongside the Covenant, and return in Halo 2, Halo 3, and Halo Wars to fill the same role. The Flood are driven by a desire to infect any sentient life they encounter, and are depicted as such a threat that the ancient Forerunners were forced to kill themselves and all other sentient life nearly 100,000 years before the beginning of Halo in an effort to starve the Flood to death.
