These super mutants were created in the "Evolutionary Experimentation Program," the experiment assigned to Vault 87. The modified strain of FEV used to create these super mutants resulted in a new strain of super mutants which, in addition to becoming sterile, grew larger and stronger as they age.
The first super mutants of this variety were created in 2078, becoming a permanent feature of the Capital Wasteland. Too dumb to overrun it, but too strong to die off.
They differ from their Western counterparts in that they possess a yellow-green skin color as opposed to the green or blue colors of their western cousins. They are also generally less intelligent and more aggressive. They also appear more healthy, as they are never seen with any cybernetic implants or organic disorders. However, unlike their distant cousins they retain less of their humanity after transformation, and no distinguishing features from their former lives can be found. Every super mutant's facial expression is permanently set in a sneer.
During exploration of Vault 87, information from terminal entries reveals more about the process that humans go through to become super mutants. When exposed to the specific strain of FEV found there, muscular and skeletal systems develop rapidly, while mental faculties diminish. Most sexual characteristics are eliminated, transforming the subject into an almost asexual state.
Despite their apparent lack of intelligence, the mutants are somehow able to organize themselves into a coordinated army (as evident from numerous raids). They have also procured large amounts of advanced weapons, ammunition and equipment, and maintain the FEV infrastructure necessary to transform humans to increase their numbers. How they are able to achieve these things is never explained, as the player never meets a mutant leader or governing body in the game, unlike in previous Fallout games.
In the ruins of D.C., the super mutants are looking for human captives in order to expand their army, as well as a new source of FEV; as a conversation between two super mutants in Vault 87 reveals that they are running out of "green stuff".
Also, as Fawkes demonstrates when retrieving the GECK in Vault 87, they are highly resistant to radiation.
Despite their seemingly low intelligence, super mutants can sometimes employ effective military tactics. Melee-armed mutants will move in to engage the player while those behind them take pot-shots with ranged weapons. Super mutants armed with grenades will often use them without regard for any fellow mutants that might be caught in the blast radius.
When encountered at lower levels, super mutants are usually in groups of two or three, accompanied by one or two centaurs. At higher levels they can be found in groups of three to five, with a few centaurs acting as their watch dogs.
These are the youngest and weakest of the Capital Wasteland super mutants. They are usually encountered in groups of two or three, led by a stronger super mutant. Regular super mutants have almost twice as much health as most standard human non-player characters, but this is somewhat offset by their lack of body armor. Some of their prime locations are the GNR building plaza, the National mall, the Capitol Building, the Statesman Hotel, the National Archives, and Falls Church. They can also be found aboard Mothership Zeta in stasis chambers. Freeing them will cause them to become hostile.
Super mutant brutes are stronger and tougher opponents than regular super mutants, as they are better armed and armored. They are most commonly seen once the player character reaches a higher level. Brutes are easily distinguished by their galea-like metal helmets and crudely stylized metal armor.
Until Broken Steel is installed, super mutant masters are considered to be the group leaders of the mutant bands which plague the Capital Wasteland. They have more Hit Points than most "common" super mutants. They are discernible by their armor, which appears to consist of what resembles black tubing that wraps around their lower and upper body and something like a fighter pilot helmet. A gas mask is strapped to their left shoulder, possibly acting as a makeshift pauldron. They are generally never alone and are usually accompanied by one or two brutes.
The super mutant overlords are variants added to the game in Broken Steel. They are aged, even more powerful than super mutant masters, and much harder to bring down. Super mutant overlords appear to be evolving into behemoths, and are about half-way between the normal super mutants and behemoths in size. Their intelligence (in comparison with other types of super mutants) is questionable, but they are smart enough to wield Energy Weapons with some degree of skill. Sometimes, they are seen leading groups of other super mutants, although they are more frequently seen in pairs, if not completely alone. Overlords also have a 40 unblockable damage bonus when attacking with a tri-beam laser rifle and a 25 damage bonus when attacking with a special version of a super sledge. When carrying an assault rifle or a Chinese assault rifle, they use a one-handed pistol animation. They have a good chance of dropping above-average loot such as stimpaks, mini nukes, and purified water. They appear frequently at later levels. One will appear the first time the player travels to the GNR Building.
Towering above any player character, at about 20 feet tall, the behemoths are the greatest threat to humanity found among the Super mutants. There are only five known behemoths to be found in the game so far, although reports of their sightings continue through dialog with the Brotherhood of Steel.
These super mutants are the oldest and strongest of their kind. As well as being many times larger than any other humanoid creature, for unknown reasons, they will not speak; instead they will make monstrous roars. They are usually armed with an almost unrealistically large fire hydrant mounted on a large pipe; other than that, they also use their enormous fists. Either way, both weapons are heavy-hitters, and will cause major damage against any enemy smaller than them.
If a super mutant picks up a pistol, it will use the same attack animation as an assault rifle, which is a two-handed grip (the front hand is floating in front of the pistol). When shooting the pistol, their hands will shake from the recoil, as if the pistol were automatic.
There is a conversation between two super mutants in which they discuss "the green stuff" (FEV) and that Fawkes thinks that men will come to take it away, while his companion says that they will turn the intruders into mutants.
Super mutants are not hostile towards giant ants or even mirelurks, but one can be seen fighting a pack of feral ghouls in the depths of Farragut West Metro Station. As can be proven by talking to Willow outside Underworld, non-feral ghouls are left alone by the mutants. This, in turn, is contradicted by the random encounter "ghoul friends" where they claim that they "couldn't make it past the super mutants".
Informing Elder Lyons that the super mutants originated from Vault 87 can gain you some Positive Karma.
After Broken Steel is installed, super mutants become rarer, and finding them will take some effort outside of spawning areas. Some super mutants can be heard talking that the "bucket heads" have been killing too many of them, this being their nickname for the Brotherhood of Steel.
pcps3xbox360 Occasionally, super mutant brutes, masters and overlords may appear merely labeled as a "super mutant", but still have the same health and equipment of brutes/masters/overlords. [verified]
pcps3xbox360 Super mutants may not acknowledge the player no matter how close he/she gets to it. [verified]