Feral ghouls are creatures found throughout the Commonwealth and Maine in Fallout 4.
Having infested most of the Commonwealth, the standard feral ghoul can be encountered nearly everywhere, especially in areas with heavy traffic, such as near train tracks, and especially within the city.
The degeneration into a feral state (referred to as ferocious post-necrotic dystrophy) is not fully understood. It is known that it is a result of a degeneration of the brain (which is not affected by the regenerative mutation of the spinal cord) and emerges following the atrophy of higher brain functions, accompanied by an increased level of aggression and appetite. When the loss of capacity for thought is complete, a ghoul is considered feral. The factors that may cause a ghoul to enter this state are unclear, but anti-social or isolated ghouls are more susceptible to it. Exposure to intense radiation may also be a factor – feral ghouls have no body heat and emit lethal levels of radiation, indicating that feral ghouls are for all intents and purposes dead, their functions sustained only by their high irradiation. This allows them to survive for centuries, relying only on the energy provided by radiation – at the expense of a horrifying, emaciated appearance. Understandably, the process is irreversible.
These long gone, decaying sacks of flesh run the gamut, from being little more than a nuisance to a hardy and stalwart opponent. Ferals are typically found anywhere that is abandoned, including metro stations, office buildings, factories, and town ruins.
Feral ghouls are encountered in three distinct ways: simply wandering around, camouflaged among the rubble as they sleep, and by occasionally falling out of cracks in the walls and foundations of buildings. Once disturbed however, they growl and scream to alert other ghouls in the vicinity, causing them to attack in packs, viciously rushing and pursuing whomever or whatever disturbs them. The ability to crawl out of the walls allows them to quite easily flank and outmaneuver their targets.
The most important feature is that feral ghouls will reflexively duck and dodge incoming fire while closing distance, making automatic weapons or explosives a preferred method of dealing with them. Furthermore, ferals will not be stopped if they lose a limb or two. If they lose their legs, they crawl. If they lose their arms, they just keep on coming to slam their bodies into and bash their skulls against the attacker. The only way to kill them is to deplete their hit points. Feral ghouls have the ability to climb low fences and drop down from height if it means they can get to their prey.
Feral ghouls appear in Fallout 4 and its add-ons Far Harbor and Nuka-World.