Mutants are creatures within The Witcher series that have been changed in some way from their original form. However, a creature is no longer a mutant when it becomes something else entirely. A Witcher is a mutant form of human, but a Striga is simply a magical creature born of a curse, it changes so greatly it can no longer be considered whatever it was before. As well a mutant does not have to be born of magic, creatures that simply evolve in abnormal ways are also classified as mutants. Currently there are no real known groups of mutants aside from the Witchers whom which are low in number anyway.