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FNV nightkin.png
LocationNew California
Mojave Wasteland
VariantsMariposa super mutant

They serve the Master. They bring the pain of healing to the world. Angels in the Night, who redeem the world by bloodshed. Curiosity is a foolhardy emotion, but doubly so when it comes to the Nightkin. That is your only warning. I have much to do now. Away with you.


Nightkin are the apex of super mutant development and an example of what Forced Evolutionary Virus II is capable of achieving given the right subjects and conditions. Their history and background are an inseparable part of the broader history of Mariposa super mutants.

The nightkin are special super mutants, representing the Master's vision of a new man (sterility aside, of course). They are the toughest, fastest, and most intelligent super mutants created in the vats of the Mariposa Military Base. They were provided with the best in weapons, armor, and training that the Unity could provide.


The following section is transcluded from Forced Evolutionary Virus. To modify, please edit the source page.

In humans, phenotypical changes brought upon by the Mariposa strain are substantial, accomplished by recursive growth patterns integrated in FEV. In order for the mutation to succeed, the subject needs to have a low level of radiation-induced damage[1] and should not have been exposed to the mutated FEV in the wasteland.[2][3] Subjects that do not meet these criteria will suffer a massive overhaul of the body's systems, leading to organ failure and an extremely painful death.[1][4]

The average super mutant is 3.2 meters tall and weighs in excess of 350 kilograms. Muscle accounts for over 75% of body mass, while bone and tissue are 10% each. Fat mass is exceedingly low, accounting for between 3-5% of body mass.[5] The increased muscle and body mass lead to a change in posture: FEV super mutants have a characteristic, hunched stance. The skin tone changes substantially and becomes gray with tints of light green, though as the mutant ages, it may become more green or even olive. The skin becomes much thicker and resistant to trauma, including cuts, bruises and damage from fire, acid or even gunfire.[5] Despite this resistance to trauma, completely destroyed tissues cannot be regrown, and will result in permanent scarring or organ loss.[6]

These changes are uniform across mutants, due to the aforementioned growth patterns and pre-programmed DNA loaded into the virus. This also has the effect of removing secondary sexual statistics, in favor of a pre-programmed masculine body shape. Primary sexual characteristics, such as the penis and testicles in males and the uterus and ovaries in females are unaffected.[7] However, super mutants are sterile, as FEV perceives gametes as damaged DNA and corrects them, resulting in sterility.[5][1]

Increased size of neural transmitters and synaptic receivers in the body give super mutants acute reflexes and heightened senses.[5] However, these changes are usually not accompanied by a similar rise in intellect. The FEV strain in Mariposa has a chance of modifying intelligence: while most people retain their pre-dipping intellect,[8] a majority of the remaining group experiences a loss (typically by 30%),[5] while the remaining minority of exceptional individuals may even experience an increase.[8] The loss is the result of damage caused by recursive growth and increase in brain mass, which may be accompanied by disfigurement and damage to existing neural patterns, causing loss of memory.[1]

The most stunning effect is practical immortality. Although theorized to only bring an approximate 10% increase in life expectancy,[5] the FEV strain in Mariposa results in a cell regeneration rate that exceeds cell death rate and prevents DNA degeneration through aging. The Hayflick limit is believed to have been completely overcome. This allows a super mutant to live for centuries, though if care is not given to exercising one's intellect, elder mutants may suffer from onset of dementia and Alzheimer's disease.[9] Death is made even more unlikely by the fact that super mutants are immune to common diseases[10] and radiation.[11]

The nightkin share all of these characteristics with their brothers. They differ in that they are the perfect fulfillment of the mutation, with the highest level of strength, resiliency, and their intelligence retained or even enhanced by the process. Subsequent alterations to their biology were caused by prolonged use of Stealth Boy technology. The stealth field caused permanent recoloration of their skin pigment, to a gray blue color. More importantly, it has caused neuro-chemical changes to occur in their brains, leading to mental instability and disorders, including schizophrenia, delusions, and even split personalities.[12][13]

Their personality is an interesting element. Their superiority resulted in the development of an arrogant, borderline chauvinist streak in many, not helped by the preferential treatment they received. As nightkin developed their mental disorders, however, their personality slowly changed. They slowly started to lose tolerance for being seen, relying increasingly on their Stealth Boy to remain invisible to the naked eye, fueling a vicious cycle of cumulative mental damage.[14][15]


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Notable nightkin


The nightkin are the top level enemy super mutants found in the game. They are encountered as enemies on the upper levels of the Cathedral and within the Los Angeles Vault. Many also patrol the wastes around the Mariposa Military Base. The ones within the Cathedral are notable for being equipped with the aforementioned Stealth Boys (whose effect is purely cosmetic).

Fallout 2

The nightkin don't appear in the game under the name, but roving groups of die hard super mutant marauders, remnants of the Master's Army, are encountered in the wastelands of the Central Valley, commonly shouting phrases associated with the nightkin.

Fallout: New Vegas

For the first time, nightkin appear as distinct characters with their own unique look and armor. Hostile nightkin are commonly found wielding rebar clubs, miniguns, incinerators, super sledges or, in the case of nightkin masters, and bumper swords. Notable nightkin include:

Uncharacteristically for NPCs, nightkin have the Toughness and Ninja perks. Interestingly, while Boone's Spotter perk does not work with cloaked nightkin, ED-E's Enhanced Sensors does.

Van Buren

Gray paragraphs are based on Fallout: Brotherhood of Steel and were not confirmed by primary sources. Few nightkin were scheduled to appear in Van Buren. Only Revelation John was confirmed to be intended for the game, in New Canaan.

Fallout: Brotherhood of Steel

Gray paragraphs are based on Fallout: Brotherhood of Steel and were not confirmed by primary sources. Nightkin formed the core of Attis' army and the primary executors of his plan to reestablish the Unity and continue the Master's plans. They were equipped with next generation stealth suits, offering them the same capabilities as Stealth Boys.

Behind the scenes

  • The mutant commando advanced character class from Fallout d20 was based on the nightkin role in the Master's Army.
  • Nightkin have an obsession with the brahmin, manifesting as worshiping a skull (Davison), killing them to stop their mooing (the Chupacabra), and a lone nightkin attempting to sell "wind brahmin" (tumbleweeds) near a tumbleweed ranch.
  • Joshua Sawyer conceived of the Nightkin becoming schizophrenic from Stealthboys and was directly inspired by The Invisible Man and his progression into insanity by taking an invisibility drug.[16]



  • PCIcon pc.png Some nightkin can bug out and become untargetable. They can only be damaged through collateral damage or by NPCs.

Fallout: New Vegas

  • PCIcon pc.png The shaders can bug out and cause the nightkin to remain invisible even after they reactivate their Stealth Boys.
  • PCIcon pc.png PlayStation 3Icon ps3.png Xbox 360Icon xbox360.png If the Chupacabra is killed, the player may encounter a separate nightkin master in the middle of Novac, an erroneous respawn of the Chupacabra.



Nightkin appear in Fallout in the Cathedral and the Mariposa Military Base, in Fallout 2 as a hostile encounter on the world map, in the Secret Vault in Fallout: Brotherhood of Steel, and make a comeback in Fallout: New Vegas and the add-on Dead Money. "Nightkin" also occasionally appear in the password list when hacking a terminal in Fallout 3.


  1. 1.0 1.1 1.2 1.3 The Vault Dweller: "{120}{}{How does the Virus work?}"
    ZAX 1.2: "{157}{}{My research into the Forced Evolution Virus, or FEV, indicates that it is a shifting-absorptive virus. It copies DNA patterns much like RNA, storing these patterns in exons.}"
    "{158}{}{These exons, combined with the FEV, are re-injected into the host cells in typical viral infectious fashion. This causes the host cells to 'regenerate' their DNA.}"
    The Vault Dweller: "{159}{}{How do you catch FEV?}"
    ZAX 1.2: "{162}{}{FEV is not 'caught', per se. It is not air-transmittable. Typically, infection is through injection, or direct physical contact with an FEV sample.}"
    The Vault Dweller: "{164}{}{Why isn't FEV affected by radiation?}"
    ZAX 1.2: "{166}{}{The FEV is a megavirus, with a protein sheath reinforced by ionized hydrogen. It is therefore capable of absorbing neutrons without becoming radioactive.}"
    The Vault Dweller: "{168}{}{If the FEV re-infects the host with its assimilated viral patterns, how does it make a 'better specimen'?}"
    ZAX 1.2: "{169}{}{The FEV is pre-programmed with introns of corrected DNA appropriate to the proper type of species. It therefore attempts to correct the DNA of the individual.}"
    "{170}{}{However, as the FEV is partially reliant upon the DNA of the individual, and also includes portions of its own recursive code, the effects can be unpredictable.}"
    "{171}{}{When inoculated into an individual with significant genetic damage, such as through radiation, it will cause the body's systems to suffer massive overhauling, leading to organ failure and death.}"
    "{172}{}{In a genetically viable individual, it re-writes portions of DNA, causing accelerated mutation, usually leading to recursive growth due to the FEV's own patterns.}"
    "{173}{}{This recursive growth leads to an increase in muscle and brain mass, but is often accompanied by disfigurement and damage to existing neural patterns, causing loss of memory.}"
    The Vault Dweller: "{174}{}{What potential long-term side effects exist?}"
    ZAX 1.2: "{178}{}{As the FEV causes constant regenerative update to DNA, it would effectively render the subject largely immortal, as cell death would be offset by augmented growth.}"
    "{179}{}{Additionally, as the gametes of the reproductive system consist of 'half-cells' using split DNA, they could be perceived as 'damage' by FEV, which would 'repair' them, rendering the subject sterile.}"
    "{180}{}{However, as my laboratory facilities are damaged beyond repair, this is conjectural. I cannot offer physical proof. You will have to, in human terms, 'take my word for it.'}"
    The Vault Dweller: "{181}{}{Could FEV mutation be corrected with a counter-virus?}"
    ZAX 1.2: "{184}{}{No. FEV does not retain unaltered original copies of the subject's DNA. Only a virus which re-infected the subject with original DNA could reverse the effects. Additionally, there is no known way to remove the FEV itself.}"
  2. The Vault Dweller:"{188}{}{Why am I a prime human ?}"
    Lieutenant: "{194}{LIEUT30}{The FEV was mutated by the war radiation. Those living in this desolate wasteland have been exposed to this mutant FEV, essentially inoculating them from the full effects.}"
    The Vault Dweller: "{195}{}{So?}"
    Lieutenant: "{197}{LIEUT31}{So, you're from a Vault and have limited exposure to this mutated virus. The original FEV in the Vats should work quite well on you.}"
  3. Fallout Bible 0: "6. According to Chris A., the ghouls in V12 were exposed to radiation and FEV. I know Harold said the Vault door opened early or something, so the radiation bit makes sense. My question is, how were the ghouls of Vault 12 exposed to FEV? Harold was a special case, since he went to the Vats with... er... someone, whose shall remain nameless... and got dipped. How do you account for the others? - Richard Grey"
    "When the West Tek research facility was hit, it shattered the FEV storage tanks on levels four and five and released the FEV into the atmosphere. Through some means, perhaps propelled by the explosion, the virus was able to reach the ghouls quickly and the mutation process began even as the radiation was rotting away their bodies. How the virus was able to survive the blast without being sterilized is unknown... it would depend on what type of warhead cracked the West Tek facility like an egg.
    Actually, Harold never said he got dipped (although it's possible). He was exposed, however - being in close proximity to FEV is enough to cause mutations, as the Enclave slaves mining Mariposa discovered. I imagine the shield between the vats and the control room in Mariposa was meant to keep the virus contained."
    Note: The West Tek Research Facility is an underground bunker, which although was directly hit by a nuclear weapon did not release the Forced Evolutionary Virus. The FEV was moved to the Mariposa Military Base (a bunker under a mountain) before the Great War.
  4. Fallout Bible 8: "Peter Hopkins asks:
    I was reading version 5 of the Bible, and found a bit of a conflict with current knowledge... In one of your anwers, it was said that it was random whether the FEV increased intelligence or not. However, as far as I know, FEV increases the growth and integrity of ALL cells consistently, by doubling the amount of genetic material in the cells. In this case, an increase in brain size (assuming a healthy brain to begin with) and intelligence should be regular. Another theory could be that, as the mutant's brain grows, the mass of the mutant's body increases exponentionally and the brain would not be big enough to control the whole body and sustain the throught process of a human body. Also, it is possible that while intelligence does increase initially, the brain does not gain the resistance to radiation that the body does, and the mutant develops brain damage and shows reduced intelligence. Are any of the above true? PS There is a very good report documenting the effects of FEV and how it was developed on the No Mutants Allowed message board ( PPS I don't know about any so called 'purists', but i am hugely interested in the fallout world and would love to FOT background in the Bible.
    About FEV:
    That might be why some of the super mutants (such as the Lieutenant) are smart (or remain smart) - but generally, for some reason (I don't know off the top of my head, nor do I know if it's spelled out anywhere), they're about 30% dumber than a normal human being, if Vree's research disk in the Brotherhood of Steel is accurate. I wouldn't be surprised if the dipping process caused brain damage in dipped subjects - it's a hell of a shock to the system.
    Furthermore, everyone's favorite introspective machine intelligence, Zax, has the following to say about it:
    When inoculated into an individual with significant genetic damage, such as through radiation, it [FEV] will cause the body's systems to suffer massive overhauling, leading to organ failure and death. In a genetically viable individual, it re-writes portions of DNA, causing accelerated mutation, usually leading to recursive growth due to the FEV's own patterns. This recursive growth leads to an increase in muscle and brain mass, but is often accompanied by disfigurement and damage to existing neural patterns, causing loss of memory.
    Other possible factors that might be causing the super mutants' stupidness:
    - Most mutants have some degree of radiation poisoning, which may cause problems and brain damage, as mentioned above.
    - The process is unsafe - the mortality rate on "dippees" is pretty high. This is likely due to radiation poisoning.
    - Memory functions are "sometimes" impaired by the dipping, and intelligence loss may occur as well. Harold's memory wasn't in the best of shape after exposure.
    From the Pre-War experiment tapes, it looks like some mammals did display consistent increased intelligence (raccoons), while others didn't (the dogs) or even suffered brain damage (the chimps and the seizures). However, in an old Scott Campbell doc, there was a note that later subjects injected with the FEV (especially the chimps) hid their enhanced intelligence from their captors (or in the case of the raccoons, made a break for it).
    Furthermore, the FEV tests at West-Tek were done through injection, not dipping, so it's possible the dipping process itself that causes the brain damage. Possibly with the increased brain mass in the skull, the brain is "squeezed," and all that tasty juice runs out the ears.
    Still, on the other hand, a lot of the animals Grey talks about in his experiment tapes that were running around the Military Base were getting smarter from the FEV, and he himself became supra-intelligent.
    So there's a long-winded series of random answers. Moving on!"
  5. 5.0 5.1 5.2 5.3 5.4 5.5 Vree's autopsy report
  6. The cybernetic implants, branding scars, and the amputated tongue of Lieutenant, Dog and God, and Mean Sonofabitch respectfully are examples of permanent tissue damage.
  7. The Vault Dweller: "{132}{}{You can't possibly take on the entire world.}"
    Master: "{134}{Mast10}{I'm not after the world, yet. When I turn your fellow vault-dwellers into mutants, my forces will be too strong for any to stand against! But don't worry, you won't care. Care! Care!}"
  8. 8.0 8.1 Fallout Bible 5:
    "5. In F1 the Lieutenant said that the FEV raises intelligence. There are, however, very many dumb mutants. What can you say about it? And what do you think of my theory, which i've been using in my Fallout PnP campaign?
    Sorry, Pawel, for two things: I wasn't able to personally respond to your email because I kept getting bounced, and two, I wasn't able to comment on your FEV theory (as a reminder, I can't read fan-created material, so just send questions, comments, or facts if you can).
    As for the FEV enhancing intelligence, the original Pre-War FEV at West Tek did, and more consistently than the Fallout-era virus.
    The current Fallout-era FEV does enhance intelligence - in some people. Just not many. The Lieutenant was one of the lucky ones who didn't become a knuckle-dragging, butt-scratching moron after being dipped (and it may not have raised his intelligence, he may have been that smart before his dipping, but no records of his past exist to verify this).
    The FEV that was released out in the wasteland was mutated by radiation, so its effects changed. As for the FEV at Mariposa, the Lieutenant says the super mutants are smarter than humans ("We are highly intelligent and immune to disease"), which is only half-right, and he also says that the virus can also interfere with a person's memory, causing them to forget things. Obviously, the Lieutenant keeps forgetting that most of his super mutant forces can barely form complete sentences.
    Basically, the FEV in the vats only has a small chance of raising a being's intelligence (or even keeping it intact). The Master was one of the lucky ones. More often than not, it causes brain damage. It's also possible that the crude dipping procedure in Mariposa also caused imperfect mutations as well, reducing the chance of heightened intelligence.
    But to answer your question: the FEV at West Tek before the war caused increased intelligence in its subjects, but the FEV at Mariposa after the war rarely enhanced the intelligence of humans who were dipped. The reason for this is unknown.
    Chris Taylor says:
    Chris Taylor: Actually, a dip in FEV has a chance of modifying Intelligence, but it doesn't always increase it. Some people do gain increased intelligence, a larger majority lose intelligence and most people remain the same. It also depends if people have enough radiation damage to be turned into ghouls or super mutants."
  9. Broken Hills mutants (Mutant miner, Old mutant), and those appearing elsewhere, are long lived, but some show signs of impaired cognitive function.
  10. The Vault Dweller: "{141}{}{How are you more advanced?}"
    Lieutenant: "{149}{LIEUT14}{Intuitively obvious to the most casual observer. We are highly intelligent and immune to disease. The strong survive! It is our goal to improve the human race.}"
  11. The Master: "{168}{Mast27}{Your humor will not save you now. Do you accept my offer, or not? Not! Accept!}"
    The Vault Dweller: "{169}{}{Not.}"
    The Master: "{171}{Mast28}{Radiation has no effect on us. The FEV virus makes us immune. Your argument is weak, and so are you.}"
  12. The Courier: "What are you working on?"
    Henry: "The Nightkin have varying degrees of mental instability due their addiction to Stealth Boy use. I've been trying to come up with a cure. I'm currently investigating the local Nightstalker population since they seem to have developed a natural stealth field. I've also gotten my hands on a working Stealth Boy Mark II prototype, but that experiment is riskier. I'd rather not pursue that research just yet."
    (Henry's dialogue)
  13. The Courier: "What makes you think that the Nightstalker mutation isn't natural?"
    Henry: "I've compared the brain chemistry of a Nightkin to one of the local Nightstalkers we killed. They both exhibit similar neurochemical changes. Now, I'm not claiming that Nightstalkers are running around wearing Stealth Boys, mind you. I just don't think it's all a coincidence."
    (Henry's dialogue)
  14. The Courier: "What's wrong with the Nightkin?"
    Marcus: "Nightkin suffer schizophrenia from the Stealth Boys they're always using. One of the reasons I settled Jacobstown was so they could be cured. While they're in town, the Nightkin aren't allowed to have Stealth Boys so their craziness doesn't get worse. Trouble is the Nightkin don't like being visible, either. They don't take being exposed too well."
    (Marcus' dialogue)
  15. The Courier: "Why are the Nightkin here in Jacobstown?"
    Keene: "The Stealth Boys we use have cumulative, adverse effects on our minds. Jacobstown was supposed to be a sanctuary, a place to find a cure. Instead, we wait and wait. I'm sick of waiting."
    The Courier: "Why are the Nightkin here in Jacobstown?"
    Keene: "The Stealth Boys we use have cumulative, adverse effects on our minds. But, thanks to you, it seems a cure is on the way at last."
    (Keene's dialogue)
  16. Q&A session with Josh Sawyer during a live charity stream. (reference begins at 8:32:55)