Ghoul

Ghouls or necrotic post-humans are decrepit, ragged, almost rotting, zombie-like mutants, victims of massive radiation poisoning. They usually speak with very raspy voices.

Origins
Limited exposure to radiation for a longer period of time sometimes causes humans with an unknown genetic characteristic to transform into ghouls, although rare cases of faster transformations into ghouls are also not unheard of. Exposure to radiation typically results in sickness followed by death for the average human being. The genetic x-factor that will lead to mutation into a ghoul upon exposure instead of the typical deadly outcome remains unknown.

Most known ghouls in the Core Region were created from vault dwellers living in Vault 12 under the city of Bakersfield (better known as Necropolis after the Great War). As part of the vast Vault Experiment Program, the Vault 12 door was designed not to close properly. Thus, massive amounts of radiation attacked those within the Vault, most of whom either died or mutated, eventually turning into ghouls.

Ghouls from other regions most likely originate from other, similarly ill-fated shelters that shielded their residents from radiation enough for it not to kill them, but not enough for them to remain unscathed. There are ghouls in the Midwest, most notably a nuke-worshiping cult in Kansas City (other towns with some ghoul population are Quincy and Springfield).

In the Capital Wasteland, many ghouls currently alive were born long after the Great War in 2077 and succumbed to radiation poisoning much later, due to the high levels of radiation in Washington, DC and its surroundings for decades following the fall of the bombs. Moira, the Megaton shopkeeper who gives the Wasteland Survival Guide quest, is a notable example of this (if the player decides to destroy the town of Megaton, she is found ghoulified outside the entrance after the bomb is detonated). The majority of intelligent ghouls in the Capital Wasteland have chosen to settle in Underworld, a settlement of ghouls established in the Museum of History in the DC ruins on the National Mall. The settlement got its name from the fact that the ghouls established their town in a part of the museum that was hosting an exhibition on mythological representations of the afterlife on the day the Great War began and the bombs hit Washington.

Confusion over origins
There is some controversy even among the makers of Fallout games about the origins of ghouls. While Tim Cain said explicitly that ghouls are only a result of radiation, consistently with the science of the 1950s, Chris Taylor said that a mix of both radiation and FEV was in play. While Chris Avellone initially supported the latter view in his Fallout Bible, he was later convinced to support the radiation-only version , which is also confirmed in Fallout 3.

Biology
Ghouls created in the Great War of 2077 were still alive during Fallout (2161), Fallout 2 (2241), and there were even a few remaining in Fallout 3 (2277). All ghouls live longer than normal humans. The reason for this longevity has to do with differences on the cellular level, and the ability of ghoul DNA to regenerate at a rate unmatched by normal human nucleic acids. In a ghoul, sometimes, additional genetic material is added as a result of the mutation. The unnaturally long lifespan of a ghoul is also due to a mutation within the autonomic nervous system of certain individuals following exposure to specific combinations of ionizing radiation with wavelengths below 10 picometers. Radiation that has such a short wavelength, less than 10 picometers, is known as gamma radiation and is normally lethal to healthy humans in even moderate doses. The mutation in response to gamma radiation that produces ghouls disrupts the normal process of decay in the neurotransmitters along the spinal cord.

Ghouls were not created immediately after the Great War in 2077. The process took months or years. After a few weeks their skin slowly started to flake off and crack. In Fallout 3, Carol in the ghoul settlement of Underworld explains that even after the War it took a while for the ghouls to start to look as they do now.

Specifically, the neurotransmitters affected in a ghoul's mutation are those responsible for cardiac and respiratory function in a healthy human being. These transmitters are continually regenerated at a greatly accelerated rate after the mutation sets in, carrying sufficient oxygen to sustain the life of the subject while being insufficient to retain dermal elasticity and avoid the resulting necrosis (much like what happens during the course of the disease once called leprosy), the result of which is the decaying, corpse-like appearance of post-mutation humans.

Ghouls are generally as intelligent as normal humans. However, their physical repulsiveness makes the life of a ghoul difficult at best - only the most tolerant human communities accept them as anything more than monsters. Some ghouls eventually go mad after the continuing decay caused by further radiation exposure has effectively destroyed their cerebral tissue and are called "feral ghouls"; these mindlessly aggressive--and hungry--zombies give all ghouls a bad reputation. These feral ghouls create the misconception amongst regular people that they are zombies like those depicted in old horror films, only alienating intelligent ghouls further from "smoothskin" humans.

Ghouls are, naturally, immune to most forms of radiation still remaining in the Wasteland. Radiation poisoning cannot really get worse for the ghouls, though it can hasten the process of decay and lead to their decline into the feral state as described above. However, many ghouls report feeling healthier when exposed to low-level radiation, and thus make their homes near locations with acute background radiation. The ghouls known as "Glowing Ones" actually enjoy large amounts of radiation, which they describe as being "comfortably warm".

Feral ghouls
Feral ghouls are those of the unfortunate mutants that lost their minds and became aggressive. Their intelligence is almost completely gone and they react mostly on instinct, making them basically fast-moving carnivorous zombies. They are, however, still non-aggressive toward other ghouls. If you have the ghoul mask this will make all feral ghouls ignore the player unless they get very close or engage in hostile behavior.

Glowing ones
Some ghouls absorbed so much radiation that they glow in the dark. They are called the Glowing Ones and are often considered outsiders even by other ghouls. The Glowing Ones also emit radiation, so they can be dangerous to normal humans.

This variation also takes much more punishment than their feral counterparts. People have seen on more than one occasion a feral Glowing One fighting or being chased by "normal" Feral Ghouls.

Born ghouls
Through cruel experimentation on humans by Dr. Sebastian at the Reservation, Born Ghouls were created. They are ghouls who were not mutated humans, but who were actually born into ghoul-dom.

Quotes

 * There ain't any ghouls but old ghouls. We're all sterile, see, but we're incredibly long-lived. We're the first and last generation of ghouls. - Typhon
 * Without medical technology, all of us Ghouls are going to die off in the next 20 years, anyway. - Gordon (Gordon dialogue file)
 * [Say, how do you make a ghoul?] With silver-bells and cockleshells and… Boy, you are dumb, aren’t you? Severe radiation. That’s how. How do you think? You know, many bombs go boom, flash of light and heat, flesh burns off, but you don’t-quite-die-type severe radiation? - Wooz (Wooz dialogue file)

Appearances
Ghouls have appeared in every Fallout game.

Behind the scenes

 * A ghoul is described as "Bloodman" in an old Fallout concept art.
 * In Fallout 3, Feral Ghouls bear resemblance to Iron Maiden's mascot; Eddie the Ed. Where 'normal' Ghouls bear a resemblance to horror-punks, the Misfits' Crimson Ghost. Roy Phillips face is very similar in particular to Misfits' singer, Ben Graves stage make-up.