Highlights

  • The Flood, a parasitic organism in the Halo universe, is the most threatening enemy type with the capability to wipe out entire species.
  • The Flood's origins date back to the Precursor-Forerunner War, where a sentient powder became corrupted into the parasitic organism.
  • Despite being defeated in the past, the potential for The Flood to return remains as there are still specimens scattered across the galaxy.

The Halo franchise is home to some of the most iconic enemies in all of video game history. Evolving with each Halo entry, The Covenant takes center stage in the original Halo trilogy and most of its spinoffs, with most Halo media being set during the Human-Covenant War or shortly thereafter. Elites, Grunts, Brutes, Drones, and Jackals, The Covenant has no shortage of instantly-recognizable foes at its disposal, but there's one species in the Halo universe that poses a greater threat than all of The Covenant's forces combined, and that's The Flood.

First introduced towards the back-half of Halo: Combat Evolved, The Flood is a parasitic organism that needs to consume sentient life in order to survive and grow. In the video games, The Flood act as a zombie-like threat that hits hard but can be taken down fairly easily, but in Halo lore, The Flood are a lot more terrifying, capable of wiping out entire species in the blink of an eye. The Flood are undoubtedly Halo's most threatening enemy type, and though they've technically been wiped off the face of the galaxy, their return is still possible.

Halo Combat Evolved Cover Retro
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Halo Might Not Be Done With The Flood Just Yet

The Flood's Origin

Over the last few decades, The Flood's origin in the Halo universe has changed a few times, but the most recent version takes fans all the way back to the Precursor-Forerunner War, set at least 200,000 years before the start of the original Halo trilogy. According to the novel Halo: Silentium, in the final days of the ancient war, the Precursors - in a last ditch effort to preserve themselves against extinction - turned themselves into a sentient powder, with plans to hibernate for thousands of years and eventually become strong enough to take their revenge. However, this powder became corrupted, and became the parasitic organism now known as The Flood.

The Forerunner-Flood War

Though technically first encountered by the original human species (before the Forerunners were forced to wipe every species from existence and start again), The Flood became the primary adversary of the Forerunner empire, the leading force in the galaxy. When conventional military weapons didn't stop the mass spread of The Flood, the Forerunners turned to experimental, highly-advanced weaponry, creating Sentinels, and eventually, the Halo Array. 12 ring-worlds, the Halo Array was designed to wipe out The Flood by eliminating its food source, thus cleansing the entire galaxy of life, but not before the Forerunners could create copies of every living species to be released back into the galaxy upon The Flood's defeat.

The Flood's Return and Second Defeat

Though the Forerunners were successful in their eradication of The Flood, the parasitic horde would return about 100,00 years later when the UNSC and Covenant brought their war to Installation 04, one of the surviving Halo rings. Here, both The Covenant and UNSC stumbled upon an underground Forerunner research facility, where a handful of Flood specimens had been waiting patiently for their inevitable release. Though the Master Chief managed to destroy Installation 04 and The Flood on it, the UNSC super-soldier encounters the threat once again on Installation 05, and this time the forces prove to be too overwhelming for both the UNSC and Covenant.

After spreading across the ring-world and evolving into a Gravemind, The Flood use the UNSC ship "In Amber Clad" to transport themselves to the Covenant space station High Charity, where they proceed to wreak havoc on its occupants. A little while later, The Flood crashes the now-corrupted High Charity onto The Ark, and the Master Chief and Arbiter are forced to fire a newly constructed Halo ring to eradicate the threat once more, barely making it out alive.

How The Flood Could Come Back

While The Flood has been defeated yet again, the history of Halo's universe proves that it won't stay down for long. There are still plenty of Forerunner rings, Shield Worlds, and research facilities scattered across the galaxy, and presumably there are a few Flood specimens left in each one, meaning that another breakout is more than possible in the near future.