The Flood is a parasitic alien creature that appears in the popular first-person shooter series, Halo. This organism is focused on killing and absorbing every sentient creature it can find, similar to that of a common zombie.


The Flood first appeared over 10,000 years B.C.E (Before Common Era, or just B.C.), when the alien organism attacked several Forerunner-controlled planets and proceeded to infect nearly every living thing it could find.  This led to a long war spanning several decades and resulted in the fall , before the Iso-Didact, a Forerunner commander/general, activated the Halo Array, a series of ring-shaped weapons whose goal was to deprive the Flood of its food supply: sentient beings.  The Array did this by generating a pulse that killed all sentient organisms it touched, and, when combined with the remaining Halos, annihalated all non-protected life in the galaxy, including the entirety of the Forerunners with the exception of the Ur-Didact.  This effectively rendered the Flood starved, with the exception of trace colonies established on certain Shield Worlds and captive test groups sent to specific Halos for study by Forerunner Monitors, the guardians of the Halo weapons.  One of these test groups escaped and eventually overtook the Monitor of Delta Halo, or Installation 05.  This resulted in the complete takeover of the area around the Library of Delta Halo, what is now known as the Quarantine Zone.

A milenia later, in 2531, the UNSC Spirit of Fire, a human warship following a Covenant signature, stumbled upon a massive Flood presence on Shield World 0459, a relic of the Forerunners meant to protect sentient life there within a micro-Dyson sphere, or, in the case of 0459, a hollow interior that protected occupants from Halo effects.  The Flood biomass here had caused a complete takeover of the surface of the installation, and trace colonies were scattered across the interior.  These colonies included a Proto-Gravemind, the basic developing brain of that Flood colony. This colony was destroyed alongside Shield 0459 when Spirit of Fire detonated her faster-than-light Slipspace drive inside the planet's artificial sun.

21 years later, in the year 2552, a human spaceship, named the Pillar of Autumn, stumbled upon Installation 04, the first Halo to be discovered by humanity, when the Autumn made an emergency Slipspace jump away from the under-attack colony of Reach.  Here, Spartan Sierra-117, or the Master Chief, stumbled upon that Halo's Flood subjects, who had been unwittingly released by the Covenant.  These subjects eventually spread throughout the immediate regions of the installation.  The Master Chief resorted to destroying the Pillar of Autumn, now crashed on the surface of Halo, by detonating the engine cores, which resulted in an explosion that fractured the ring into desolate segments after the fires reached over 1,000,000 degrees Fahrenheit.

Several weeks later, the UNSC In Amber Clad, along with the Master Chief, discovered another Halo (Delta Halo). Coupled with the ignorance of the 05 Monitor, 2401 Penitent Tangent, the Flood subjects on the installation escaped, and caused a complete takeover of the area surrounding Delta Halo's Library.  After Master Chief killed the Prophet of Regret, he was knocked unconcious by a Covenant ship's plasma bombardment and was taken captive by the Flood.  It was discovered that the Flood Gravemind, a sentient organism comprised of the minds of thousands of hosts, was present in the depths of Delta Halo. This Gravemind was later destroyed when the Mater Chief activated the replacement for Installation 04 before completion, destroying the replacement and the Gravemind, as well as decimating the surface of the Ark and splitting the UNSC Forward Unto Dawn in half during the Master Chief's escape with the Arbiter.  There has been no contact with any Flood resistance since the Gravemind's destruction.


The Flood is operated by a single hivemind-like creature known as the Gravemind.  This joint organism is formed from the minds of many different hosts.  Similar to the way ants work, the Gravemind commands all Flood colonies within reach, often on several planets.  It sends orders in a drone-like fashion to infected hosts, who then work to complete an objective.

Infection Form

The Flood comes in many different forms.  Mutations occur quite often, typically when a Gravemind is established.  These "pure forms" are created purely from Flood biomass and do not require a host.  The most common forms of Flood are Infection forms.  These organisms are a small form of Pure Flood, and are the most typical forms of infection.  Similar to Half-Life's Headcrabs, Infection Forms jump onto a potential host and latch onto any possible grips with it's legs.  The Infection form then proceeds to burrow into the victims chest with its tentacles, which sprout blotches of biomass and result in a complete takeover of the host's nervous system and motor functions, as well as increased mobility (long jumps) and limited use of weaponry.  These Infection Forms often group into large swathes, capable of overwhelming even the most resilient of attackers.  Other forms of Flood infection are through spores, which, when breathed through the lungs of a host, suffocate and infect the victim.

Combat Form

The second most encountered form is the Combat Form.  These organisms consist of an infected host occupied by an Infection Form.  These combatants often grow long claws sprouting from the host's wrists and hands, and the heads of the victims are often deformed and misplaced.  For example, the Elite Combat Form.  The head of the unfortunate host is turned fully around in the socket and nearly encased in biomass, and the chest in completely covered over.  The Human Combat Form has its head popped out of its socket and frozen in a scream or just dangling open.  These Combat Forms have limited use of weaponry, often those that were in the hands of the host. These forms are quite formidable combatants, and should be approached wearily.

Carrier Form

The third and one of the most dangerous forms is the Carrier Form.  This form of the Flood is often encountered deep within Flood-controlled territory.  It is an infected host that is bloated and deformed with Flood biomass, forming a sort of hollow cocoon.  A dozen or so Infection Forms can be contained within this cocoon, thus the name "Carrier Form."  Two long, squirmy tentacle-like arms project from the biomass, and two slightly more bulky, but still tentacle-like legs seem to replace the original legs.  This results in very slow movement.  When the biomass is breached to the inside, the carrier form combusts in a shower of pus and biomass, and the contained Infection Forms are then released upon the unfortunate attacker.

Pure Form

These unique Flood forms were first encountered during the Quarantining of Voi, when a Covenant cruiser loaded with Flood crashed in the African city of Voi.  The Pure Flood had the ability to morph into different forms at will. These forms were the Tank Form, the Ranged Form, the Stalker Form, the Stealth Form, the Infector Form, and the Transport Form.

  • Tank Form
    • The Tank Form is the most resilient of the Pure Flood.  The hulking creature is similar in appearance to a Covenant Hunter, though has a split midsection and a massive arm for crushing resistance, rather than a cannon.  These Flood forms were only able to be killed in one hit by a Covenant Energy Sword or a Spartan Laser.
  • Ranged Form
    • The Ranged Form is named for its ability to fire ranged projectiles at enemies.  These crystalline shards were fired from the biomass of the Flood form.  Unlike the other Flood forms, however, this one cannot move.  It can, however, latch onto ceilings and walls, and can curl up into a ball to avoid being damaged.
  • Stalker Form
    • The most mobile of the Pure Forms, the Stalker Form takes the appearance of a long, narrow animal with two large claws for attack (however this form attacks rarely, nd prefers hit and run tactics), a large maw, and two articulated legs for movement.  The tactic here is often to scale a wall or a ceiling and then transform into a Ranged Form for attack.
  • Stealth Form
    • The Stealth Form excels in its namesake: stealth.  This form is similar to the Stalker in terms of movement, and, like the Combat Form, has limited use of weaponry.  It was cut from the final Halo 3 game.
  • Infector Form
    • This Flood form is similar to the Infection Form in that it is utilized as a means to spread infection, however its primary function is to release Flood spores into the air around potential victims/hosts.  Like the Stealth Form, it was removed from the final game.
  • Transport Form
    • This Flood form is similar to the Carrier Form, with the exception of transporting several (around a half-dozen) Flood Combat Forms into battle.  Like the Stealth and Infector Forms, it was cut from Halo 3's final game.

Juggernaut Form

This massive Flood form was part of the cut content from Halo 2.  It was similar in appearance to the Carrier Form, however it was easily 3-4 times the size of the Carrier.  Unlike the Carrier, its primary focus was direct combat, and was able to jump long distances to attack a target.  This Flood form had a massive amount of hitpoints, more than the Tank Form, and was most likely cut from Halo 2 for balancing issues.  Modders were able to find the code for the Juggernaut in the game's files, and a few were even able to implement the Juggernaut into the game, albeit with a few missing pieces.

List of Appearances

  • Several Halo extended universe novels
  • Halo: Combat Evolved
  • Halo 2
  • Halo 3
  • Halo Wars


  • The Flood were a result of the Precursors, a civilization predating the Forerunners.  When the Precursors were nearly exterminated by the Forerunners, a powder was created to assist in the reformation of the species; however, time rendered the powder corrupt and it eventually mutatec with other organisms to create the Flood.
  • The exact date the Flood came to be is unknown.
  • The exact planet where the Flood originated is unknown.
  • The Flood is similar to Xenomorphs in that they use humans and other creatures as a means to spread and reproduce, as well as being an alien organism.
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