Flood pure form

The Tank Form: one of the many kinds of pure form used by the Flood.

"Alas, brother. The Flood... it has evolved!"

— An unidentified SpecOps Sangheili during the Battle of Voi

Pure forms, also rendered pureforms, are an advanced type of Flood form used when a Flood outbreak reaches a critical mass. Unlike the more typical Flood of an early outbreak, Pure forms are signified by their lack of a host body, but are instead formed from raw biomass reshaped by the Flood to suit specific tasks as-required. However, the added complexity of these forms means that they can only be created once a Flood outbreak has reached the Coordinated Stage, having accumulated significant biomass reserves and created a Gravemind to guide the wider infection.

Overview

Flood pure forms address an inevitable challenge that is faced by a substantial large-scale Flood outbreak: once a given environment has been sufficiently converted into the Flood, the amount of hosts available for conversion declines. As such, the Flood is able to offset this lack of hosts by constructing dedicated and often specialised Flood forms entirely of Flood Super Cell (FSC) - converting its victims into raw biomass to be reshaped by the Flood at will rather than simply hijacking an existing organism. This process can only be achieved if the Flood has reached the Coordinated Stage of an outbreak and constructed a Gravemind to guide the Flood's development. Pure forms have some overlap with combat forms, engaging in combat against advanced threats and aiding infection forms in securing hosts to spread the infection. However, as the outbreak grows, pure forms eventually overtake combat forms as the primary mechanism of the Flood's spread, and combat forms are retired; relegated to defensive roles, converted into carriers, or converted into raw biomass for use in propogating further pure forms.

The process of creating a pure form begins with the accumulation of calcium from assimilated host lifeforms. As an outbreak grows in scale, Flood key minds accumulate tumorous masses and mucus-like lakes of FSC: most of this mass is used to convert the environment into blightlands and Flood hives, though some is also used in the creation of pure forms. The calcium reserves are used to create a framework upon which FSC is cast, creating entirely new life forms entirely of Flood origin.

Due to this process, the number of shapes a pure form can take are theoretically infinite, and many are additionally capable of reshaping their bodies at will to suit the needs of the outbreak in the moment. However, a few varieties tend to be commonly used. The capability of pure forms to adapt to changing threats makes them priority targets for forces attempting to fight them.

Types of pure form

Shifter

Main article: Shifter

The Shifter is a name ascribed to the most commonly-seen pure form: a creature capable of transforming between three different configurations at will. They are commonly found near newly-established hives, lurking inside the lair to protect it from intruders until such time as larger and more complex pure forms can be created. They are also used to assist combat forms in direct assaults, acting as a force multiplier capable of adapting to changing threat conditions.

The three configurations a Shifter can change between are:

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  The Stalker form: a spider-like creature capable of climbing and jumping long distances to ambush prey.
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  The Ranged form: a squat, immobile creature capable of firing calcified shards of biomass at enemies.
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  The Tank form: a large. hulking behemoth akin to a Hunter capable of absorbing massive amounts of punishment.

Gaunt

Main article: Flood gaunt form

Bearing a resemblance to the much larger Abomination and Juggernaut keyminds, Gaunts are highly mobile and agile pure forms that can rapidly traverse the battlefield using their tendrils. In a combat situation, they can immobilise their opponents, making them vulnerable to attack and infection by other Flood forms.

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  The Gaunt.

Hellion

Main article: Hellion

Hellions are massive, hulking Flood pure forms that serve as an apex of the Flood's evolution. They are not keyminds, but instead serve as a sort of mobile hive and siege engine capable of incubating massive numbers of lesser Flood forms. Similarly to the Shifter, Hellions can reshape their forms at will, making them highly adaptable at countering enemy defences.

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  A Hellion.

Infester

Main article: Flood infester form

Infesters are pure forms created for use as specialised anti-vehicle Flood forms. They aggressively target any vehicle they encounter, latching onto it, boring into the hull and attacking the crew, and then promptly dying. Upon their death they spread Flood spores, ensuring the infection and conversion of the vehicle they are attacking if they are not stopped in time.

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  An Infester.

Spawner

Main article: Flood spawner form

Spawners are an uncommon kind of pure form, specifically created inside the High Charity Flood hive during its quarantine on the Ark to try and counteract the Sentinel and Banished defences surrounding the crash site. They are analagous to carrier forms, serving as mobile infection form gestation chambers that can sit in the backlines of an assault to continuously reinforce the Flood's attack with fresh waves of infectors. In noncombat situations they travel far from existing hive sites in order to propogate the Flood's spread into new environments.

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  A Spawner releasing a wave of