“The Red Plague” is a large-scale expansion MOD that brings body horror elements into Subnautica.
Its story is planned to consist of five acts, with Act 2 currently released.
The MOD adds an entirely new story centered on the mysterious infection known as the Red Plague, which is consuming Planet 4546B, transforming Subnautica’s survival experience into something deeper and far more hostile.
The Red Plague grotesquely mutates the bodies of living creatures and strips them of their original behavior,
gradually driving the marine ecosystem toward collapse.
Even normally peaceful creatures can become ferocious predators, leaving the player under constant threat of being torn apart underwater.
The player is not exempt from the threat of plague contamination.
As infection progresses, hallucinations, confusion, bodily mutations, and other terrifying symptoms begin to close in.
However, through information shared by the researchers and the development of equipment derived from plague materials,
new areas of activity and new tactics become available.
Managing contamination status, surviving encounters with deadly creatures, investigating new biomes...
The MOD demands a more strategic form of survival than anything found in standard Subnautica.
What did the Aurora witness from orbit?
What awaits in the depths of the flesh-filled caverns?
What is the origin of the Red Plague?
This is not merely a MOD built around horror effects.
It is the beginning of a new story of exploration and discovery that greatly expands the world of Subnautica.
Existing creatures mutated by the Red Plague have lost their original behavior and become violently aggressive. There is no longer any safe place on this planet.
Ruined bases where research on the Red Plague was once carried out.
Valuable resources and blueprints for powerful equipment remain within them. However, careless exploration may lead to a terrifying end.
The Mutated Diver appears as what remains of humans infected by the Plague. Even if you see “it” at the edge of your vision, do not look directly at it.
After the player lands on 4546B, they receive a transmission from Angelina, who identifies herself as an Alterra researcher.
Having been contracted as an investigator after previously being responsible for maintaining “non-essential” systems, the player receives assignments from the researcher Fred and begins investigating the mysterious infection spreading across the planet: the Red Plague.
Using construction drones, the player succeeds in building a massive quarantine dome. However, the investigation soon takes a new turn: a vast cavern emitting an anomalous signal is discovered.
The inside of the cavern is filled with lethal concentrations of plague matter, and numerous dangerous plague lifeforms roam within it. At its deepest point, the player encounters a mysterious entity calling itself “Bennett.” Following his advice, the player sets out to destroy the core of the Red Plague, known as the Plague Heart, but...
これに対し『The Red Plague』でも、プレイヤーはアルテラの研究員たちから通信で指示を受け、シャトルを用いてサンプルや物資を送付する。また、Act 1では巨大な隔離ドームの建設が物語の大きな節目となるなど、感染症、サンプル輸送、遠隔地の研究拠点との連携、惑星規模の防疫といった要素に共通性が見られる。
After this MOD is installed, creatures in the base game become infected not by the Kharaa bacterium, but by the new pathogen known as the Red Plague. As a result, infected creatures undergo visual and behavioral changes unique to this MOD.
Creatures infected with the Red Plague show major changes in both behavior and gameplay.
As stated in the story, individuals infected with the Red Plague display a marked increase in aggression regardless of species. Because of this, even normally harmless small herbivorous fish begin behaving aggressively toward the player and nearby uninfected creatures.
Infected small herbivorous fish also become impossible to catch. Since creatures such as Peepers and Bladderfish serve as important early-game sources of food and water, it is best to prepare alternative means of sustaining yourself as soon as possible.
Some creatures transform over time after infection into “plague-mutated creatures.” Examples covered on this site include the Mimic Peeper and Plagued Bladderfish, which have unique names and databank entries distinct from their normal counterparts.
Some creatures have also been observed to undergo major visual changes after infection even though they do not have unique names or databank entries.
Many details about the relationship between the Red Plague and the Kharaa bacterium remain unclear at present.
Unlike the Kharaa bacterium, which did not show visible infection phenomena in leviathan-class lifeforms, the Red Plague can infect such creatures as well and drastically alter their appearance.
However, this does not mean that the MOD is set in a timeline or setting where the Kharaa bacterium does not exist. Multiple lines and records within the MOD story explicitly state that Kharaa also exists.
It is currently unclear what kind of setting is planned regarding an ecosystem that assumes the presence of Kharaa, and how this relates to the Sea Emperor Leviathan and Enzyme 42.
Unused data contains references to the Sea Emperor and Enzyme 42 being affected in some way by the Red Plague, so these settings may be expanded upon in a future update.
This MOD has several interesting similarities with the old story of Subnautica: Below Zero that existed before the Frostbite Update.
In the old version of Below Zero, the protagonist conducted her research while communicating with the orbital space station “Vesper,” sending samples via Exchanger Rocket and receiving supplies in return. In the late-game story, a large-scale alien quarantine device was also activated, covering the sky with a blue barrier.
In comparison, The Red Plague also has the player receive instructions through communications from Alterra researchers, while sending samples and materials by shuttle. In Act 1, the construction of a massive containment dome also becomes a major turning point in the story, creating similarities in elements such as infection, sample transport, cooperation with a remote research base, and planetary-scale quarantine.
Furthermore, unused data in this MOD includes an item named “Concentrated Enzyme 42,” the same name as an item that also appeared in the old version of Below Zero. However, it is unclear whether these similarities are intentional references or influences, or simply coincidences arising from shared themes such as infection, quarantine, and sample transport.