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Super mutants are created by exposure to the Forced Evolutionary Virus II from the vats of the Mariposa Military Base in California. They represent the finest form of super mutants, far more advanced than their primitive East Coast counterparts created by imperfect strains of the virus.[1]


Super mutants were created by way of the Forced Evolutionary Virus, beginning at West Tek, mutating from humans.[2] In January 7, 2077, FEV research was transferred to the Mariposa Military Base,[2] to continue under the lead of Leon Von Felden and Robert Anderson. Vats of the virus were prepared as a basis for further development and human experimentation, with a near 100% success rate on lab animals, granting an approximately 60% increase in size and potential 200% intelligence increase.[3] The team then created the FEV-II strain, able to create powerful super-soldiers, exhibiting superior physical prowess, resistance to combat damage, aging, and disease, as well as a negligible loss of intelligence.[4]

The Master

The vats were rediscovered in 2102 by an expedition led by Harold, a major Hub merchant. Accompanied by Richard Grey, an exile from Vault City, he managed to crack the base security and infiltrate the lower levels. However, within the vats, the automated crane crashed into the two, knocking Harold out and flinging Grey into the vat with FEV. Harold woke up in the wastes outside the base, and escaped. Grey, on the other hand, underwent extreme mutation due to prolonged exposure to the virus in the vat. His intellect grew exponentially, allowing him to comprehend even the most complex issues easily.[5] Grey methodically researched FEV, experimenting with animals and eventually, captured scavengers that strayed into the facility. It wasn't until a few failed mutations that he discovered radiation could be a deciding factor in the success of the change, leading him to pick subjects more carefully.[5]

When his Lieutenant was created, he suggested a secondary reason for possible incompatibility. Reviewing available evidence, he concluded that failed mutations in relatively non-irradiated humans are caused by the inoculating effect of a mutated FEV released during the destruction of the Great War had on humans it came into contact with. While exposure to the mutated strain wasn't enough to turn the subject into a mutant, it was enough to cause complications with the pure strain of the FEV that would result in the death of the subject. Grey (now calling himself the Master) concluded that prime subjects can be found among Vault populations. Super mutants were sent to uncover sealed Vaults and capture their inhabitants for processing. This move gave the Master unprecedented amounts of human subjects and in 2137 he began to mass-produce mutants. The success rate was only 8-10%, but the Unity steadily grew.[Non-canon 1]

The number of test subjects was further increased by raids on Hub caravans and the establishment of the Children of the Cathedral in 2156. Captive caravan drivers and zealots underwent processing, both in Mariposa and Grey's seat of power beneath the Cathedral. In his lair, the Master and his staff experimented with the FEV by injecting it into the brains of the subjects (usually the pineal gland, but also the amygdalae or medulla), triggering changes in brain chemistry. These experiments have limited success: four extremely powerful psykers were created, capable of theoretically wiping out the human race.[Non-canon 2][6] FEV experimentation by the Master was abruptly halted in 2162, when he was killed by the Vault Dweller and the vats were destroyed.

The destruction of the Unity and the Master caused the super mutant community to splinter and break apart. Bands of super mutants fled into the wastes in all directions, with charismatic mutants becoming leaders of warbands and even entire armies. The bulk of the super mutants led a disorganized flight northwards, into Oregon.[7]


Named super mutants

Super mutant characters
Harry Lieutenant The Master
Vincent Viscious
Fallout 2
Elmo Francis Frank Horrigan
Gond Grundel Lenny
Marcus Melchior Zaius

Generic super mutants



  1. 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. 2.0 2.1 FEV experiment disk
  3. FEV research
  4. Vree's autopsy report
  5. 5.0 5.1 Richard Grey's audio diary
  6. Mad scientist
  7. The Chosen One: "{119}{}{So, tell me what you know about the Master.}"
    Leanne: "{144}{}{Well this might take a bit. Be a gentleman and buy me a drink, wouldn't you please? Not whiskey though, Nuka-Cola please.}"
    The Chosen One: "{147}{}{Sure.}"
    Leanne: "{149}{}{Thanks. Now let's see... I remember my mom telling me about this huge migration that happened 70... or was it 80 years ago...}"
    The Chosen One: "{150}{}{Please, go on.}"
    Leanne: "{151}{}{Really big mutants with weapons as tall as you and me came from the south. Mom said it looked like a big migration of some sort.}"
    The Chosen One: "{152}{}{How many?}"
    Leanne: "{153}{}{Don't know, but there were multiple groups of them. Some would continue north, others headed east. No one knew where they were going.}"
    The Chosen One: "{154}{}{Go on.}"
    Leanne: "{155}{}{They were quite upset and seemed to be fleeing from something.}"
    The Chosen One: "{156}{}{Really?}"
    Leanne: "{157}{}{Yeah, there were also others in dirty, tattered purple robes... they kept babbling about how the Master was dead...}"
    The Chosen One: "{158}{}{Interesting.}"
    Leanne: "{159}{}{Some of them even committed suicide right here in town!}"
    The Chosen One: "{160}{}{So?}"
    Leanne: "{161}{}{Well don't you see. They were talking about the Master, the one your ancestor killed.}"
    The Chosen One: "{162}{}{Thanks for the story.}"