Halo games follow a pattern with players facing off against the Covenant in the first act and the Flood in the second. These rampant, revolting creatures are part of a disease that spreads fast throughout a galaxy. Had the Flood exited the Milky Way Galaxy, there's no telling what could have happened to the universe.

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To contain this problem, humans and an ancient race called the "Forerunners" have tried drastic measures. By the end of this, you'll find out how the Flood were created—and why they must be stopped. They are abominations that wreak havoc in the Halo universe. These are 10 things you didn't know about the Flood.

10 The First Encounter Of The Flood Infection Was In A Powder Form Found In Cylinders

It came from seemingly out of nowhere. A substance in powder form was found in containers by early humans. They decided to feed domesticated animals with the powder. This substance would lead to the infestation of the Flood.

It also is responsible for the endangerment of Forerunners, an ancient race who is behind the construction of the Halo rings. Several ships of the powder were sent to Forerunner planets. It was the malevolent Precursors who created this life-consuming powder.

9 The Flood Infestation Originated From Domesticated Pets Called "Pheru"

Although the powder that contained the Flood was fed to several domesticated animals, the Pheru was most commonly infected. A Pheru is like a small chicken since it is a commonly eaten and has similar behavior.

They are plant-eating animals, which is why it was so disturbing to find out that Pheru ate each other after being infected. At first, the infection stayed within domesticated animals and didn't spread to humans. Credit goes to Halo Diehards member "AddiCt3d 2CHa0s" for this creative illustration of a Pheru.

8 The Flood Represents The Flood From Noah's Ark

With terms like the "Ark" and "Flood" being thrown around, it's not difficult to figure out that the Flood is a metaphor for the Flood from Noah's Ark. In Noah's Ark, the Ark is a survival vessel which saves Noah and animals from the flood.

In Halo, the Ark serves the same purpose. Several references are made to religion, including mentions in Norse Mythology and Greek Mythology. Perhaps the creators of Halo are religious. Halo's Covenant is also a spiritual reference, relating to the Holy Covenant in Abrahamic religions.

7 Man-Made Weapons Are More Effective Than Covenant Weapons Against The Flood

If you've ever played Halo's campaigns (each of them contains the Flood), you might notice that human weapons prove to be more effective than Covenant weapons. This could be because human weapons work better against enemies without shields, and plasma weapons are more effective against shields.

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Balancing made the damage difference less in later games. However, in the first two Halos, it was highly noticeable that weapons like the shotgun, assault rifle, sniper rifle, and pistol unleashed more damage against the Flood.

6 They Are Like Superhuman Zombies

The Flood as a collective species can make decisions, revealing they are capable of intelligence. Throughout the Halo series, we see developments with The Flood. They change in appearance and in behavior. Explaining the Flood to someone who doesn't know their background would be like explaining what a superhuman zombie is.

They can run fast, wield weapons, and attack vigorously during melee combat. This decrepit species is like a zombie since it wants to infect every living being in the universe.

5 Lead Mission Artist Vic DeLeon Spent Six Months On The Flood's Design And Infested Spaceships For Halo 3

Halo 3 is arguably the best Halo game in the series. Combat-wise, it had remarkable balancing, and matches were highly enjoyable. Maps like Ascension, Guardian, Bahalla, Last Resort, and The Pit dynamically shifted the online multiplayer of Halo. Sure, the series attained prominence in Halo 2, but Halo 3 was unquestionably an upgrade.

Bungie worked tirelessly to create the best game possible. Lead mission artist Vic DeLeon spent six months on The Flood's design and infested spaceships for Halo 3. Infested ships play a critical role in the story of Halo 3.

4 The Flood Was Created By The Precursors

After the Forerunner-Precursor war, which took place 10 million years prior to the Forerunner-Flood war, the remaining Precursors were driven to the outskirts of the galaxy. The Precursors wanted revenge against the Forerunners. They created a powder-like substance which went through mutations during a long period of time.

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Eventually, it started the biggest outbreak the Milky Way galaxy had ever seen. This horrible infection was discovered by early humans before it was by the Forerunners.

3 Halo 4's Flood Looks Very Different Than Previous Designs

By comparing the appearance of the above photo's Flood to other pictures in this list, you'll notice there is a tremendous difference in the Flood's appearance. Notably, Halo 4 was the first Halo game not to be developed by Bungie. Instead, Microsoft's subsidiary, 343 Industries, developed Halo 4 with changes.

A boring narrative made Halo 4 not as enjoyable as previous Halo games. It wasn't until Halo 5: Guardians that 343 Industries made a genuinely entertaining game. Love or hate the design, something about this armor makes the Flood look like Power Rangers.

2 The Flood Appeared 10,000 Years Before The Forerunner-Flood War

The Flood appeared seemingly from out of nowhere. The power substance that started the Flood was first used on domesticated animals such as the Pheru. The Pheru seemed to have better behavior until they began to show abnormalities. They began growing a strange type of fur, then the Pheru ate their fur and other animals.

This was so strange because Pheru were thought to be herbivores. The Flood demonstrated intelligence by choosing not to infect the humans—they waited until they encountered the Forerunners.

1 The Flood Brought The Forerunners To Near Extinction During The Forerunner-Flood War

The Forerunner-Flood War was a cataclysmic event that led to the extermination of Forerunner beings. The only known living survivor, the Didact, was kept in a stasis chamber where he was awakened during Halo 4. The Forerunners are known for creating the Halos, the Ark, and the structures on them.

The Forerunners reached their peak population approximately 100,000 years ago. Since the Flood had a delayed effect, they were able to populate the galaxy before revealing their hostile nature. As a result, a war waged on for hundreds of years, and it was ended with the activation of the Halo rings. The Halo rings eliminated all life in the Milky Way galaxy except those on the Ark.

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