The Flood are an ancient parasitic species that feature in the Halo game series.
The Flood were an ancient race of vicious extra-galactic parasites that were able to infect other sentient hosts and convert them into more of their kind. In the last days of the Forerunners it was believed by a number of their kind that the Flood was actually the last remnants of the Precursors.
Attempts were made by the Forerunners at finding an immunity to Flood infection. One of these was the use of the Composer though this proved to be a failure. However, the Didact decided to use it to transform his Prometheans into energy constructs that served him as soldiers in wiping out the Flood. Thus, they lost their physical forms and became mindless constructs where they followed their leaders commands which they did so willingly. The Promethean Knights were deployed in the conflict against the Flood where they proved to be effective. However, the parasite had spread too far and had greater numbers with the Didact deciding to forcibly transform humans into Prometheans for the war.
After every possible measure was exhausted, the Forerunners decided that the only way to truly defeat the Flood was to starve it of life that it consumed. Thus, they decided to wipe out the galaxy of life with the Halo Arrays and repopulate it with samples that they had safely stored.
Despite the destruction of the parasite, samples of the Flood were kept in various facilities for study as it was deemed that there were still aspects of the organism that resided outside the galaxy that could bring about its return. It was hoped that through continued study that perhaps an immunity or a cure could be discovered in these facilities.
It was designated in as Latin Inferi redivivus ("the dead reincarnated"). The Flood was a voracious hive-minded parasite that sought to capture, convert and control other sentient hosts in order to perpetuate itself. Infected hosts had their nervous systems subsumed by the parasite who turned their bodies into puppets of its will with their memories and flesh assimilated as well as twisted for further infestation. This parasitic race was considered an anomaly to all known biology with their mode of growth and reproduction making them incompatible with any natural ecosystem. It was an organism that fed on intelligent life and in doing so became ever more intelligent itself. Central to the parasite was a substance known as the Flood Super Cell (FSC) that composed their being with this being an unknown form of neuron-like cell. These cells formed the Flood biomass where they configured into any shape or muscle needed to continue to sustain the biological and organizational growth of the parasite. In the latter stages of Flood development, the super cell spontaneously generated as part of the Flood's attempts to transform the environment into one more conductive to the growth of the Flood. These cells then form spores that can parasitize other organisms whether they were sentient or non-sentient with the hosts having their bio-mass transformed into an incubator for more larger Flood forms. Each infected host was then linked to form a distributed intelligence that allowed for interstellar coordination along with the formation of further more sophisticated consciousness nodes. There was no known inoculation, treatment or cure against infection nor a means to reverse it with the only effective countermeasure being containment along with incineration.
A number of varying forms were adopted by the parasite among its infected hosts with some of these being specialized to accomplish specific goals. Its most basic version was the Infection form that were small organisms with numerous tendrils from its body that swarmed enemies in order to hijack their bodies and nervous system. Once infected, the hosts suffered a rapid transformation where they were converted into another form. For battle, the Flood twisted host bodies to create Combat forms that were used to subdue hosts and secure further targets for infections. After the completion of their ask, the combat forms were transformed into a Carrier form that contained more infection forms within it and thus further extended the parasites ability to grow in number. Following the acquirement of sufficient biomass, the ruling intelligence of he Flood began creating Pure forms. These were formed completely from assimilated nutrients and biomass with these being able to shift between three different configurations that were known as Stalker forms, Tank forms and Ranged forms. A highly specialised combat form was the Juggernauts that were directed by a seething mass of infection forms that were linked together by multiple hosts. The host's minds were harnessed by the creature whereby it analysed enemy activity and adjusted the strategy of local Flood forces. These organisms were said to hold some traits that were normally associated with fully-fledged Key Minds such as the capacity to synchronise nearby parasites along with relaying information between various Flood groupings. The most distinctive feature of these Flood was their enormous size and sheer physical strength allowing them to use their sharp tendril-arms to impale armored vehicles and crush enemies under their large legs.
It was determined that the Flood followed a four stage developmental process:
- Feral stage : the Flood were at its most simplest form where they communicated through pheromone and had an instinctual objective to harvest enough calcium to lead to the creation of a valid Gravemind.
- Coordinated stage : at this point the parasite becomes dangerous as it was now controlled by a Gravemind.
- Interstellar stage : the Flood begins to take control of space-faring technology that they used to consume the local star system and began spreading throughout the galaxy to infect more hosts.
- Intergalactic stage : a theoretical point whereby the parasite made use of all the captured technology to depart to uninfected galaxies in order to further replicate itself.
Upon reaching a certain mass, the Flood formed a construct known as the Compound Mind that controlled the deployment of the parasites. Generally, the Flood had no compunction with sacrificing parts of the whole but if the core of the Mind was threatened then it reacted violently and quickly. Such attacks against it were the only time when it parasite retracted or slowed its growth in an effort to preserve itself. Once infestation was established over an area, the parasite continues to transition from feral aggression to more coordinated conversion efforts leading to the creation of specialised Flood organisms that networked their individual intelligences. These were the Key Minds that acted as coordinators for nearby Flood forces where they harvested the wisdom from host organisms that was used by the parasite to expand, outthink and consume other forms of life. As the parasite grew in numbers then the Key minds combined to create larger and much more intelligent networks. The presence of these organisms was an indicator that most local life and sentient hosts had been consumed by the Flood. These intelligences were capable of extraordinary levels of strategic planning abilities and were a match with Forerunner Metarch-level Ancilla with thm capable of assuming complete control over captured sectors of space and sending converted battle fleets through space. Upon reaching critical mass, the seething form of the intelligent networks gave rise to a Proto-Gravemind that sifted through the memories of the infected victims. The Gravemind was considered the apex of Flood evolution that exerted control over large areas and was able to divide its attention among its various strategies on a galactic scale.
To spread itself, the Flood used large chunks of biomass as dispersal pods that spread the parasite to new locations.
The parasite could survive and grow in almost an environment though it thrived in a small range of habitable planets. Within hives, a controlled environment was made for accelerated growth but over time an entire planet's biosphere could be altered to match these ideal conditions. The first step in this conversion process was the formation of Blightlands that were areas around a hive that was filled with specialised growths that harvested the vitality of the soil. In addition, this organic mass soaked in solar energy and consumed all native life within its vicinity. These areas grew in vitality but ultimately were consumed in order to provide the necessary raw material for the city-sized spore towers along with the other array of Flood organs that bring about the demise of a planet.
A weapon used by the parasite was a logic plague that was a payload of corrupting truths and logic puzzles that induced rampancy in artificial intelligences. It operated by targeting rationality protocols and allowing the Flood's views to hold sway over an artificial intelligence's decision-making process causing the construct to turn on its creators and ally with the Flood.
- The Flood were created by Bungie as video game antagonists for the Halo games.
- Further background on their origins was shown in the Halo novels by writer Greg Bear.
- Halo 2:
- Halo 3:
- Halo Wars: