The Coordinated Stage is the second stage of a Flood infestation. During this stage, Flood population begins to rapidly increase and once sufficient biomass has been found, Pure Forms begin to be sent into combat. After this the next stage of Flood infection may begin. On the verge of initiating the Coordinated Stage, the Proto-Gravemind continues to be built until it reaches the status of Compound Mind or a Gravemind. It is at this point that the Flood becomes significantly more organized (communicating via thoughts and attacking strategically) and subsequently more lethal. Once they have gained sufficient technology, the Flood will then proceed into the Interstellar Stage.
This stage has occurred several times;
- The first was the Gravemind’s conception from the planet of G617g, the original Flood which eventually gave way to the Gravemind who made war with the Forerunners and was believed to be destroyed during the first firing of the Halo Array.
- The second occurred on the Infinite Succor, an agricultural support ship which was part of the Fleet of Particular Justice. The on-board Legate eventually became part of the biomass reserves being built on the ship by Combat Forms - it is believed to have been in the process of transforming into a Proto-Gravemind before Rtas 'Vadumee sent the vessel into the nearest star.
- Not far away on the Truth and Reconciliation orbiting above Installation 04, Captain Jacob Keyes had become an anchor for what appeared to be a Proto-Gravemind. This entity, however, had been taken care of as John-117 obtained the Captain's neural implants and the Proto-Gravemind was later destroyed by Covenant Spec Ops Units.
- At some point, a catastrophic containment failure on Installation 05 released the Flood into a Quarantine Zone, which eventually facilitated the creation of a Proto-Gravemind. This became the last known Gravemind, the one that existed during the rest of the Halo trilogy. This infestation expanded into the interstellar stage before the Gravemind and all escaped Flood forms were destroyed, reverting any Flood left in the galaxy back into the feral stage.
- This is the stage that most resembles the Flood in Halo 2.
- Although no pure forms were present in Halo 2, with the exception of the Juggernaut which still never spawns without modding, They are present in Halo 3, which is Interstellar stage.
- The Flood in Halo: Combat Evolved were always found without whatever attire their hosts usually wore. In Halo 2, however, this changed, as the Flood then kept the apparel of their hosts for protection, proving that the Flood were indeed in a Coordinated Stage.