"Halo doesn't kill Flood, it kills their food! Humans, Covenant, whatever—we're all equally edible!The only way to stopthe Flood is to starve them to death. And that's exactly what Halo is designed to do: wipe the galaxy clean of all sentient life!" --Cortana
The Halo Array is a system of colossal ring-shaped superweapons known as Halos or Halo Rings, constructed by the Forerunners. The Halos were referred to by The Covenant as the Sacred Rings and labeled Fortress Worlds and Instillations by the Forerunners and their monitors.