Interstellar Stage
From Halopedia, the Halo wiki
The Interstellar Stage is the third stage of a Flood infestation. Once the Flood has gained sufficient technology, possesse no need for further evolutionary augmentations and have conquered all planets in a given Solar System then they may progress into this setting[1]. Once this stage is reached, the Flood has consumed all sentient life and technology of many planets. With the fleets of their dead enemies, they move on to the next Solar System. After taking an entire galaxy, the Flood begins the Intergalactic Stage.
