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小説Halo: The Flood,あるいはHalo Wars第9ステージの The Floodについてお探しですか?
Inferi Redivivus (Flood)
Biological information


Physical description




Skin color

多様: 緑、黒、黄褐色(宿主による) しかし多くの宿主は茶色や緑に変色する


大幅な生理的および心理的変異、  また宿主の記憶も取得可能

Military and Political information



Inferi genus

Notable Individuals
Other Nomenclature

フラッド (英語 The Flood ラテン語 Inferi redivivus[1]"The dead reincarnated"の意[2])もしくは The Parasite[3] としてコヴナントの間で知られている、十分な生命力や認知能力をもつ知的生命体に寄生することで増殖、成長する、非常に感染力のある生命体である。 900年に及ぶフォアランナー=フラッド戦争[4]の最中、フラッドは、銀河におけるほとんど全ての知的生命体(フォアランナーも含む)の絶滅の原因であった。 人間やコヴナント(エリートグラントブルートなど)に感染し、彼らをCombat Formへと変異させてしまうため、HALOトリロジーにおいては、フラッドは最も多様な形で登場する。



フラッドは非常に適応性に優れ、危険で、繁殖力のある寄生性の生命体である。 天の川銀河のG617 g1で、フォアランナーのプライマリーパイオニアグループが最初に遭遇した。 彼らは非常に感染力があるウイルス性の細胞であり、およそ931年間続くフォアランナー=フラッド戦争の発端となる。 また、フォアランナーが銀河系の生物の多様性を守るための最後の努力として、HALO ARRAYが建設された理由も彼らにある。 全ての戦力的手段が使い尽くされた後、フォアランナーはHALO ARRAYを作動させ、結果としてフラッドの蔓延を根絶すると同時に、銀河系に存在していた全ての知的生命体の絶滅を招くこととなった。

フラッドはグレイブマインドのいないところに、均等に安定して分布している。彼らは自発的に生殖する能力に欠け、知的生命体、特に自己認識し内省力のある生命体に感染して繁殖する。この段階のフラッドの感染爆発はFeral Stageとして知られている。 During its Feral Stage, the Flood is only capable of local coordination through use of pheromone-based communication. Research indicates that the content of said messages are of very limited complexity. Individual Combat and Carrier Forms have access to the skills and memories of their host; however, once an outbreak establishes a viable Gravemind, the Coordinated Stage begins—and it is at this point the Flood becomes truly dangerous.

With the formation of a Gravemind, the assimilated intelligence and memories of consumed hosts become part of a collective consciousness, which is capable of strategic thinking and commanding individual Flood forms in an organized manner.

A Gravemind (like the Proto-Gravemind that gave rise to it) is the fusion of pure Flood Super Cells and the evolved complex neuro-system of one or more sentient entities. The control it exerts over the more mobile forms it creates is accurately likened to an entity's control over its own limbs. Ergo, during the Feral stage, control is localized at the individual level, but once an outbreak enters the Coordinated stage control is assumed by, and broadcast from, a central compound intelligence.

Although no data exists from any adequately controlled experiment, data gathered in the field suggests that if a mobile form is removed from the influence of the Gravemind coordinating its group of origin it will revert to a Feral Stage. Insufficient data exists on whether mobile forms of one Gravemind would be influenced by another Gravemind, though logic dictates this would be the case. However, because individual Graveminds are remarkably similar and are all striving for the same goal, it is likely that a distinction would be impossible to detect.

The Bestiarum states that the society of the Flood closely resembles an "utopian socialist ideal as there is no wealth, no poverty, no want, no crime, and no disease; every individual works for the advancement of the Flood as a whole". It also states that it "is unfortunate that their one overriding goal is to [butcher and consume] every other life form in the galaxy".[1]


Forerunner-Flood War編集

Main Article: Forerunner-Flood War
"It fed on intelligent life and in doing so, became every more intelligent itself. The Flood was unique, it used their very strength against them."
—Cortana on the Forerunner-Flood War.

The Flood are believed to have arrived in the Milky Way Galaxy more than 100,000 years prior to 2552[5] when they encountered the Forerunners on the planet G617 g1. The Flood used unarmed civilian assets to penetrate planetary defense groups, first striking at the Forerunner-held planet of LP 656-38 e, bypassing the Forerunner Orbital Fleet, and infesting the planet below. They soon moved to similarly infest the planet DM-3-1123b. They were perceived as hostile by the Forerunners, whose ground forces were overcome by the sheer numbers of Flood forms on the planets. While at first the Flood demonstrated a lack of even "basic cohesion", they had "numerical superiority"; billions of forms dedicated to the assault, and every member of the Forerunner population a potential Flood host. In desperation, the Forerunner's armada was ordered to immediately commence full planetary bombardment on infested worlds, although at a great cost - many Forerunners were unable to be evacuated before bombardment commenced, leaving the Forerunner military with shallow victories against the Flood. In events where the naval garrisons were unable to commence bombardment, major Forerunner population centers appeared to activate localized weapons of mass destruction, effectively committing mass suicide, but stopping the growing infestation.

Thereafter, the Forerunners realized that ordinary naval tactics were unable to stem the growing tide of the Flood, and decided to pin their hopes of defeating the Flood on super weaponry. While the Forerunners initially deployed the Sentinel robotic drones to fight against and contain the Flood, almost immediately afterward, the Forerunner Fleet Command contemplated "Premature stellar collapse": using naval battle groups to destroy planetary star systems' primary stars in supernova that would engulf the planetary systems and prevent any possibility of Flood infection.

While the Flood were exponentially growing, spreading from system to system with the intent to infect the Forerunner population, not to wage war with Forerunner battle groups, the tide was turning: the Flood had reached sufficient proportions to create a Gravemind form, a creature that embodied a collective sentient intelligence for the Flood species, and one that could coordinate the Flood swarms in intelligent attacks against the Forerunner Fleets. The Forerunners were aware of this, and constructed the Contender class artificial intelligence Mendicant Bias in an effort to destroy this centralized Gravemind and disorganize the Flood. This too failed since Mendicant Bias went rampant and joined the Flood cause to destroy its former masters.

The Forerunners began a "Conservation Measure", researching the Flood, while constructing an Artifact to generate a slipspace portal leading to the Ark on Earth and possibly other uninfected home worlds of Tier 7 races they considered "worthy".

The Forerunners employed many, many measures, including intricate naval tactics in an attempt to contain the Flood, which ultimately failed. Finally, the Forerunners were forced to a Pyrrhic solution, building seven ring-like super-weapons, known as Fortress Worlds or Halos, across the galaxy. Because the Flood were parasitic, and their survival was directly linked to the presence of potential hosts, the Forerunners reasoned that eliminating all potential Flood hosts, that is, all sentient life forms in the galaxy, would "render the parasite harmless", as explained by the Forerunner AI 343 Guilty Spark. After all countermeasures failed, the Forerunners activated the Halos in 97,448 B.C, unleashing galactic destruction, and destroying almost all sentient life forms in the Galaxy. However, the human race and many other species throughout the galaxy survived the firing of the Halos because they were safely spared on the Ark which was out of range of the Halo Array or protected by the Shield Worlds, which were also out of range .

The Flood were contained, and unable to reproduce due to lack of hosts, and eventually died out. The only surviving specimens were contained in state of the art, high-security Forerunner research facilities, such as the Halo Installations and the Threshold Gas Mine.

The few surviving Covenant soldiers left were scattered and disorganized, and put up little resistance to the new Combat Forms created from numerous Covenant corpses. It is presumed that the Covenant occupants of the research facility had moved through the structure in hopes of finding Forerunner artifacts, and had inadvertently released living Flood specimens. Knowing full well what the Flood are capable of, the Covenant forces promptly locked the facility down and evacuated all personnel who survived the Flood's escape. Keyes and his team were unaware of this fact, however, and proceeded to delve deeper into the facility, ultimately coming across one of the unopened Flood Containment Chambers. Believing it was a weapons cache of some sort, they unlocked the door, and were promptly attacked and assimilated by the Flood inside. With a large supply of "edible" sentient life now occupying the ring, the Flood began to multiply and infest most of Halo. Soon, the infestation proved too great even for Halo's automated military force, the Sentinels, to handle, and the ring's commanding AI, 343 Guilty Spark, was forced to call upon a "Reclaimer" (John-117) to activate the array once more. Hearing of the above events, John-117 was deployed to the area on the drop ship Echo 419, proceeding into the facility, only to find out that most of the Marines he had been assigned to rescue had succumbed to the Flood.

These events brought the knowledge of the Flood to the UNSC. In a war of losses, this was another grim revelation for humanity.

Earth, The Ark, And The Flood's Defeat編集


UNSC Marines being infected by the Flood.

""Child of my enemy, why have you come? I offer no forgiveness... a father's sins pass to his son.""
Gravemind on the level Cortana
""I am a timeless chorus. Join your voice with mine, and sing victory everlasting.""
—Gravemind on the level Floodgate
""Of course, you came for her... We exist together now, two corpses, in one grave.""
—Gravemind on the level Cortana

At the conclusion of the Battle of Voi, with the Prophet of Truth activating the Artifact and the Jiralhanae fleet escaping to the Ark, a Flood infested Covenant cruiser appeared out of Slipspace, having penetrated the Elite's blockade of High Charity and crash landed into the city of Voi in an effort to spread. In order to prevent the Flood from escaping and infecting the entire planet, Miranda Keyes ordered John-117 to detonate the cruiser's reactors and search the ship for Cortana, causing the city of Voi to be destroyed and the Flood there eliminated. As John-117 and the Thel 'Vadam fought their way to the ship, the Shadow of Intent arrived and deployed Sangheili task force to aid UNSC marines. SPARTAN-117, with the help of the Sangheili, was able to battle through the Flood forces, including the newly encountered Flood Pure Forms to reach the crashed cruiser where he found a message from Cortana. Upon this discovery, 343 Guilty Spark arrived pledging his assistance to the Reclaimers. With the Flood spreading, SPARTAN-117 boarded a Phantom while the Sangheili went on to glass the infected areas. The remaining Sangheili forces, fulfilling their mission of removing the Flood from Earth, retreated back to the Sangheili Carrier, the Shadow of Intent, along with Cortana's message and Guilty Spark.

With the assistance of 343 Guilty Spark, Cortana's message was repaired, revealing a solution to the Flood menace on the Ark. To Lord Hood's disapproval, Miranda Keyes led UNSC forces allied with Thel 'Vadam's and Rtas 'Vadum's Sangheili's through the Portal.

On the Ark, while attempting to lower the shield surrounding the Ark's citadel, the infested High Charity made a Slipspace jump and smashed into the Ark, releasing the Flood inside the structure and causing an infestation on the newly built replacement for the destroyed Installation 04. After retrieving Cortana from the derelict High Charity, SPARTAN-117 was able to kill all Flood present on the Ark and the replacement Installation 04 by first destroying High Charity's reactors, causing a massive explosion and the destruction of the wrecked city, then activating the unfinished Halo using the Index Cortana retained from the first Halo. The ring's activation also presumably killed the Gravemind.


With the Gravemind destroyed, and all the Flood on the Ark gone, it is probable that the Flood still exist on the other Halo rings, excluding Installation 05 (although it is possible that not all of the Flood on Installation 05 left and there are still some there, since Installation 05 was never destroyed), or any other remaining Forerunner Installations. The fact that the Flood were never originally from this galaxy further complicates the issue, and how they arrived leads to more possibilities. It may be that is why the Forerunners preserved some Flood for research on the Halo rings instead of destroying them all, since the Flood would return sooner or later, and it would be better to fight a researched enemy rather than a foreign one. At least for the moment, the Flood are seemingly defeated.


Flood wall.jpg

A wall covered in heavy Flood biomass: evidence of advanced infestation.


The Master Chief stepping in Flood Biomass as he enters the Flood infested High Charity.

The Flood, a virulent species of parasites, is an anomaly in all known biology, and an anomaly to regular life. Due to this, it is thought to be an extragalactic species, originating from different galaxies[verification needed]. It is extremely adaptive, and mutates hosts through different stages of accelerated "evolution", where the body of biomatter accelerates its own evolution to the point of a massive biological breakdown, where by the infection can first take place. The virus can reproduce through asexual methods, though this is described as a last ditch effort, and only performed by pure Flood forms.[verification needed]

The only known pathway for Flood reproduction and survival is by the infestation and assimilation of other species. They do this through a form of cellular reproduction known as lysogenic replication where the viral cells infect host cells with their own genetic code which mutates the host cells into viral forms.

Capable of surviving extreme environments ranging from -75 to +53 degrees Celsius and even underwater (in early stages of life), the Flood can withstand harsh environments of all known colonized planets.

It would seem that the Flood can infest any living organism, but that they prefer hosts with a large brain capacity to accelerate the formation and expansion of the Gravemind hive intelligence and the Flood intelligence as a whole. They are only as intelligent as the beings they infect; the more cunning the enemy, the more dangerous the Flood will be.

As the Flood spread and replicate, they will alter the environment to better suit their needs. This takes the form of biomass growing on any available surface, and the air being filled with spores. This appears to be part of the Flood life cycle and is done automatically, and leads to the development of a Gravemind and a Flood Hive.

The Flood seem to thrive in moist and humid areas, which lends itself to the fact the the Quarantine Zone is bereft of organic life, and is cold and perpetually snowy, to hinder the development of the Flood.


Infection forms selectively target other species that possess sentient intelligence and are of sufficient biomass, and can infest living or lightly wounded dead bodies. Infection forms have long tendrils that pierce the skin of the host and find their way to the spinal cord. From here they synchronize with the host, matching frequencies with the host's nervous system and taking over brain functions, completely rewriting the psychology of the creature to the ravenous and voracious psyche of The Flood, although retaining higher-level cognitive abilities, such as combat techniques and technical knowledge which may be useful. However, resistance of the host is completely destroyed, as the original mind's memories are systematically erased, leaving only a simplistic and primal urge to assimilate other species and destroy them. During the early stages of infestation, when the host still retains its original consciousness, there are distinct somatosensory sensations: first the host's extremities grow numb and their lungs feel heavy.[6]

Then, the greater Flood intelligence begins to take over the mind, and sensation becomes increasingly indistinct: the host's vision seems to be "a gauzy white haze", but the host can make out shapes[7] and the host can hear a low droning through the ordeal. Finally, once physiological mutilation occurs, the host can vaguely feel dramatic changes to its own body: the limbs feel to the host as if they are made of a spongy liquid and the lungs itch as well.[7] However, the host can still control their limbs to some extent if the neurological contact with the infection form is weakened. They can use the vocal cords of Jiralhanae's, Humans, and Sangheili's to communicate as well as the moans they use as observed on The Covenant where the drop pod crashes into the third shield tower.


While baseline neurological assimilation is the same regardless of host species, The Flood's infestation includes physiological mutilation, which is species-specific.

Higher-level species capable of combat, such as Humans, Jiralhanae, or Sangheili are selectively infected to become Combat Forms. Combat Forms retain the general profile of their original species, although they are significantly mutated. Organ-based systems' physiology are corrupted, organ-specific functions are decentralized, and body cavities are decayed, making hitbox-selective incapacitation impossible; organ functions are decentralized, thus, decapitation does not down a combat form. Furthermore, highly area-specific munitions, such as sniper rifle projectiles, are completely ineffective, as picking off selective areas of a combat form leads to no wide-scale physiological impediments, and the projectile will punch through the decayed flesh rapidly, exiting through the other side of the combat form without consequence.

Combat forms also generate tentacles very quickly without regard for the skeletal structure of the host, with tentacles protruding from the combat form at odd locations, typically localized to the chest axial regions, such as the neck, armpits, or torso. A single arm is oftentimes mutated to a claw like or tentacle-like structure that splits into multiple angular, hand-like structures replacing the hand's usage, yet it will still be there. The musculature of the combat form dramatically changes as well, and the form is given prodigious arm and leg strength, allowing for heavy blows with its arm-like structures and for incredible speed and jumping height with its legs. The Flood are also prodigious climbers, able to scamper on walls with little hindrance to the organism . Metabolic requirements, however, appear to be extreme on the organism: blood vessels become extremely prominent on the surface of the Combat Form, with thick and distinct blood-colored vessels spawning all across the creature's surface, most prominently so on the head.


Flood Eat.jpg

A Marine being attacked by an Infection Form.

There is no confirmed way to effectively stop a Flood infection when an Infection Form attacks a host. However, two possible exceptions are known. One of which is to contract the fictitious disease "Boren's Syndrome", a neurological condition where radiological exposure causes electrical anomalies in the host nervous system that is actually caused by biologically enhancing drugs, such as those used in the ORION Project. The neural frequencies of the host are scrambled, although without major negative manifestations to the host. However, it has been suggested that during Flood infection, the infection form is unable to tap into the host's nervous system to kill them. It is unable to proceed to a large-scale physiological mutation, not understanding why. Although Flood DNA is sliced into host DNA, even imparting the host with increased regenerative capabilities. Avery J. Johnson, having Boren's Syndrome, escaped the containment facility where The Flood attacked two squads of UNSC Marines. However the Boren's Syndrome was to cover his past in the ORION Project, and that the Boren's Syndrome explanation was invented to hide it. In the novel Halo: The Flood, Cortana uses an electrical charge which she generates from Master Chief's suit to destroy an infection form that was attempting to infect him.

While Boren's Syndrome left untreated may leave the victim immune to the Flood, leaving it untreated usually equates to death within a couple of years. There is said to be a one in a billion chance that research, from someone so inflicted with Boren's Syndrome in a way that they cannot be infected, could be carried on to produce a cure.

Since the Flood is a parasitic life form, they depend on other organisms for survival. Thus, the only logical foolproof way to eliminate them permanently is to take away their food sources. The Forerunners attempted this by bombing large population centers, but this was seen as one of their last resorts and as such was performed too late in the war to make much difference. The absolute last resort was the use of the Halo installations, which effectively destroyed all life in the galaxy and starved the Flood. However, the Forerunners' plan included some measures to preserve sentient life and return them to their home planets, allowing the Flood's "food source" to persist, while at the same time specimens were kept for analysis on Halo Installations, allowing the threat of the Flood to be merely forestalled, not eradicated.

Environmental stimuli seem to have an effect on Flood metabolism. Halo installations typically artificially incorporate low temperature into environments suffering Flood outbreak and to create natural obstacles to Flood progress, regarded as Quarantine zones[8]. At least one Flood Research Facility used low temperatures to keep its specimens inactive and dormant as it studied them. This may be the reasoning behind keeping Installation Control Rooms in low degree weather, impeding their occupation by the Flood. The Flood are also vulnerable to temperatures on the other end of the spectrum. Plasma weapons will burn through them, as well as Sentinel Beams, indicating that the Forerunners had determined energy weapons to be the best 'basic countermeasure' available to fight the Flood. It may be a side-effect of the Flood's conversion of the body into biomass, breaking down cellular integrity and increasing flammability.

Combat Behavior編集


The Flood emphasizes "numerical superiority" in engagements and also aggressive swarming tactics.

While possessing an unusual sentient intelligence, with Combat Forms still retaining extremely high-level cognitive functions such as vehicular operation, lower level cognitive abilities, precise dexterity, and overall battlefield tactics, are notably lacking in the Flood, especially in their psychological and combat behavior. While the Gravemind coordinates Flood strategy on a galactic scale, small encounters are not coordinated between individual Flood warriors.

The Flood follow a zealous and ravenous strategy with little target selectivity, aggressively attacking all hostiles in range. Furthermore, Flood tactics are based primarily on asymmetrical warfare: the Flood uses all types of its different forms to kill the enemies that it sees. Usually the Infection, Combat, Carrier, and Tank Forms rush the enemy and attempt to quickly eliminate them. The Ranged Forms try to support their zealous comrades with ranged attacks. The Stalker Forms attempt to transform into a Tank or Ranged Form. The Combat Forms also utilize any weapon that they have picked up. While this strategy is observed to be a Zerg Rush, they aren't completely suicidal, since they usually dodge dangerous ordnance.

The Flood have a strong preference for close-range combat: combat forms possess abnormally strong melee attacks by whipping their tentacles, capable of dropping a SPARTAN-II MJOLNIR armor’s shields in half with a single hit. Carrier forms cause tremendous devastation at close ranges, and their explosions are extremely devastating to friends and foes alike at close range, with the added benefit of disseminating infection forms in the immediate vicinity of enemies. Infection forms are capable of attacking only at point-blank ranges, exploding in damaging bursts when meeting an opponent's personal energy shields or instantly grabbing hold of an unshielded enemy organism and infecting it. Combat forms can also use firearms, and have been seen clutching them in one of their hands (regardless of whether it is one-handed or two-handed). However, combat forms are extremely poor warriors at range with ranged weaponry: it is believed that the neurological ramifications of Flood infection significantly decrease accuracy, as well as weapon recoil if held in only one hand. The Flood are mostly only dangerous with heavy weaponry, such as the M19 Rocket Launcher or the M90 Shotgun, and are curiously ill skilled with close-quarters weapons such as the Energy Sword. However, it is still possible that a Flood with a Energy Sword can kill a fully shielded Elite or Spartan in one blow.

However, as mentioned previously, the Flood demonstrates a curious higher intelligence despite their poor combat aptitude and coordination. The Flood collectively learn any general information a species possess, even if only one member of that species is assimilated. For example, during the ill-fated raid on the Infinite Succor, after even one Sangheili was assimilated, all the Flood could open any doors and access any system on the ship immediately afterward, demonstrating that the Flood can share collective knowledge across their species. Furthermore, when the Flood assimilated the Prophet Legate, the Flood reflected the high-level knowledge of the Legate through its individual organisms to Special Operations Commander Rtas 'Vadumee, mocking him with the words, "the Forerunner could not defeat us...what chance you?". The Flood, however, reflect unusual knowledge in the individual psychologies of its individual species in processes facilitating increased infestation: The Flood were sighted gathering bodies in the corners of the Covenant ship Truth and Reconciliation, perhaps making it easier for Infection Forms to find hosts to reanimate. The Flood were also gathering body parts for a new Brain Form aboard the Infinite Succor.


Typical Flood combat behavior: ravenously targeting the nearest enemy, with infection forms running ahead of combat and carrier forms.

Flood Combat forms have been sighted crudely operating Ghosts, Warthogs, Wraiths, and Scorpions in ground operations, although with slow deliberation and clumsy driving and accuracy. The assimilated crewmen of the UNSC Frigate In Amber Clad were also able to initiate a Slipspace micro-jump for the frigate and perform rudimentary maneuvering of the In Amber Clad, navigating the frigate from the atmosphere of Delta Halo to High Charity and then crashing the vessel into a tower, releasing Pelican dropships to rain down upon the capital.

The Flood's millennium of existence are believed to have made the assimilation process unusually brief: creatures killed in a short firefight can be reanimated within seconds to minutes by an infection form, and live creatures can be mutated into fully grown and mentally devious combat forms within minutes of contact. The mutations can occur randomly, or uniformly: according to the Halo Graphic Novel, they can sometimes develop into engorged combat forms notably larger than the normal combat form, or can alarmingly grow thick shells within minutes, indicating that the Flood can facilitate tremendous and exaggerated metabolic activity during the physiological mutilation. Furthermore, in rare cases, the mutations can constantly shift: when Rtas 'Vadumee battled his comrade-turned-combat form Bero 'Kusovai aboard the Infinite Succor, 'Kusovai continued to mutate throughout the duration of the battle. Though never seen, it can be assumed infection forms were involved in infecting victims in this case. Before being killed to prevent his becoming a Flood, one of the Sangheili accompanying Rtas 'Vadumee appears to have a wound in his chest that may have been the entry point for an infection form. Many of the Flood on the Succor seemed to constantly be mutating the infected biomass and also seemed to merge them together. This suggests the possibility that over time any infected host can mutate further and further, as exemplified by the Brain Form or the Gravemind and different versions of the Combat Form.


  1. 引用エラー: 無効な <ref> タグ。「bestiarum」という名前の引用句に対するテキストがありません
  2. Halo.Bungie.Org: Updated and abbreviated list, errors amended
  3. The Heretic: Thel 'Vadamee: "Noble Hierarchs, surely you understand that once the parasite attacked-"
  4. Two Betrayals, first cut scene, referenced by 343 Guilty Spark
  5. Halo 2, level Sacred Icon
  6. Halo: The Flood, page 175
  7. 7.0 7.1 Halo: The Flood, page 197/198
  8. Halo 2, Quarantine Zone (Level)
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