LF.Xx.3273 [FSC]

Latin Species Name:
Inferi redivivus
Extra-galactic, Origin Unknown
Technology level:
Native Tier 7/Adopted Tier 2
Avg. Height Range:
Varies depending on host
Avg. Weight Range:
Varies depending on host
Threat Level:
Significant to Serious


The Flood is a vicious, extra-galactic parasite capable of seizing, converting, and controlling sentient hosts in an effort to perpetuate its kind. The Flood is considered one of the greatest threats to galaxy-wide biodiversity ever and were the reason the Forerunners devised and ultimately activated Halo, wiping out nearly all sentience in the galaxy.


During the twilight of their civilization, a handful of Forerunners were convinced that the Flood was actually the last remnant of an ancient race of beings--Precursors, the original creators of both humans and the Forerunners. Approximately ten million years prior to the prodigious and legendary Flood War, the Forerunners had violently and preemptively eradicated the Precursors in fear that they were being targeted. The last vestige of the Precursors was a single being and a material which eventually found its way to ancient humans and then to the Forerunners. The Flood was later held in stasis on research facilities for testing, eventually leading to several outbreaks. It is believed all outbreaks were contained successfully.

Flood Super Cell

The Flood is a virulent, parasitic life form originating from and composed of “Flood Super Cells” (FSC), a previously unknown neuron-like cell. These cells (LF.Xx.3273) form the Flood biomass, which can be configured into any shape or muscle necessary to continue and sustain the biological and organizational growth of the parasite. In the latter stages of Food development, the FSC can also be spontaneously generated as the Flood attempts to transform the environment into one more conducive to the growth of the parasite.

Transformation Process

Any significant Flood infestation has always originated with spores or microbiological vectors infecting both sentient and non-sentient species. Eventually the infection transforms into a parasitic strain, causing a sentient agent to convert their biological mass into that of the Flood’s. During this process, a pod-like creature which can vary in size is manufactured containing the necessary form, function, and matter to convert other potential hosts. Though it is not the only way one can be infected, this form is often referred to as an infection form.

Infection Forms

Infection forms, while the most unstable and fragile of Flood forms, are still incredibly dangerous. The infection form is a soft, pod-like carapace standing roughly 90 to 130 centimeters tall. It has numerous tentacle-like appendages serving its locomotive needs and a series red-frond, sensillum-like appendages that act as sensory antennas, honing in on potential hosts. Once an infection form locates a host, it violently attacks them, burying a barb-like appendage into the victim that transmits the virulent FSC. The effect varies though it often results in the “death” of the victim until the FSC takes hold, reviving them into another form—the combat form.


Combat forms, in most cases, look recognizably similar to their original host. While the host’s body is used, all control has been relinquished, transforming the body into an agent of the Flood. Some of the host’s knowledge and muscle memories are retained in order to aid in the Flood’s growth through the use of available weapons, vehicles, equipment, and even starships. Combat forms maintain the red-frond, sensory antennas of infection forms, which become the creature’s ad hoc central nervous system until it has been completely consumed by the FSC.

Carrier Forms

Carrier forms evolve when the host body starts spontaneously generating infection forms in a bulbous, mass on its back. Eventually, this mass becomes too large to manage and explodes, launching infection forms out to continue the Flood collective’s efforts to dominate their immediate location.

Coordinated Stage

The first indicator of the coordinated stage is found in the atmosphere, as the FSC propagates spores and creates a hive-like carapace holding a warm, humid environment at its center. Most Forerunner containment facilities have artificial weather modulation systems allowing it to generate resistant climates (usually cold, frigid ones), which effectively counteract and slow the Flood’s growth. While environmental conformity is one goal as the Flood speeds toward the coordinated stage, it is not the central focus. The formation of a Gravemind, a centralized intelligence or “Compound Mind,” is necessary in order to continue growth. The rise of a Gravemind usually indicates that the local host species has completely transitioned into the Flood collective and sentient biodiversity has ceased.

Pure Forms

With no remaining local hosts, entry into the coordinated stage is assured while simultaneously becoming a self-damning factor. The lack of viable “food” means that the Flood’s ability to perpetuate their various forms independently has come to an end. With the conversion of the environment and the existence of a centralized intelligence, the Flood can now spontaneously generate new pure forms as well as pure infection forms. The later transpires only if a resurfacing of uninfected sentience occurs. Decoupled from the disadvantages of the host species, the distribution of Flood at this stage is vast and nearly impossible to effectively catalog, particularly since many can spontaneously change into another form at any given time.

Future Growth

After a Gravemind has been fully established, the local Flood infestation will make efforts to leverage any technology and knowledge available to leave their current domain in search of others to infect. This is referred to as the interstellar stage and is only superseded by the Transgalactic stage, when the Flood collective is unified and large enough to move from one galaxy to the next. Effectively, this can only occur when thousands of individual, interstellar stage collectives have uniformly coalesced, spiraling toward the galaxy’s center in a harmonized pattern that ensures no population centers go uninfected.


During ancient humanity’s first encounter, it is believed that they developed a cure but refused to give this to the Forerunners. The latter eventually resorted to using wide-effect, cross-phased neural displacement (Halo) to wipe out all sentient life (potential hosts) in the galaxy. A belief in the future success of a cure, however, caused the Forerunners to preserve Flood specimens, protected by monitors on various installations throughout the galaxy. Ultimately, this may have been a mistake as it resulted in the resurgence of the Flood in the mid-26th century, as well as the arming of all surviving Halo installations.

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