Greater North American Wasteland
Forced Evolutionary Virus
The Forced Evolutionary Virus (FEV) is, aside from environmental radiation, the major source of mutation in the Fallout universe. Most importantly, both Super Mutants and the Master are the result of infection by the FEV. Aside from Super Mutants, the Master also created a variety of other aberrational creatures using the virus. FEV gave birth to a wide variety of dangerous creatures, which have became a threat to post-war humanity. Among these creatures are the super-mutants, centaur. It is also speculated that it has played some small part in the growth of irradiated creature like radscorpions, giant ants and rats, and even the creations of ghouls, though again this is only speculation.