Consumed by sadness and rage, the spirits use pyreflies to assume a warped physical form. Each fiend is a reflection of the person they were in life in some form ranging from an embodiment of their greatest desire to an appearance reflecting a misdeed. There are also fiends that came into existence without being alive to begin with, as well as living creatures categorized with fiends, like Cactuar, who are simply a part of a life cycle of desert cacti.