The Mutants are a multitude of enemies that serve Jed Stone to kill Edward Carnby in Alone in the Dark III. They are a tougher version of the normal undead and are usually unarmed. Similarly to the undead, they also turn into a feline-like animal or a bat when defeated.
The Mutants are most likely convicts (judging by their clothes) that built Jed Stone's water tank, railroad station and sewers. Their bizarre appearance may be due to the radiation emitted by the odd mineral ore that was discovered by Hutchinson.