First created by the Master and later reproduced by the Enclave, super mutants are mutated humans, products of infection by the Forced Evolutionary Virus (FEV). They are much taller, bulkier and more muscular than pure strain humans, have (mostly) green, grey, or yellowish skin, are immune to disease and radiation, and are gifted with superhuman strength and endurance. Although they are completely sterile, the rapid regeneration of their cells caused by FEV makes them virtually biologically immortal (but not immune to death from injury).