The Interstellar Stage is the third stage of a Flood infestation. Only when the Flood have gained sufficient technology, possess no need for further evolutionary augmentations and have conquered all planets in a given star system, then they may progress into this stage. Once this stage is reached, the Flood has consumed almost all sentient life and technology of many planets and with their fleets, they move on to the next star system. After taking an entire galaxy, the Flood then enters the Intergalactic Stage. This is most likely the stage the Flood was in throughout the majority of the Forerunner-Flood war. In Halo 3, the early phases of this stage are seen after the Flood consumed much of the sentient life on Installation 05, and more importantly the millions of Covenant in the city of High Charity.