Most types of underworld mythology fall into one of two basic categories: underworlds segregated based on the deeds a person performs in life and underworlds intended for all of the dead regardless of actions in life. Many of the oldest legends and myths about various underworlds fall into this latter category, and many cultures had early concepts of an underworld in which all of the dead would gather as ghosts or shades. There are also a number of instances of underworld mythology, though, in which the dead would go to different types of places depending on how the person lived or died.
Underworld mythology typically refers to any type of mythological system dealing with the location that people’s spirits or souls go to after death. While the name “underworld” indicates the idea that this was a place located beneath the real world, this was not always the case and is simply used as a single term for different systems. Some types of underworld mythology are built around the idea that the dead would go to a land beneath the land of the living, and entrances to such places could be found in certain caves. There were also mythologies in which the underworld was a reflection of the world of the living, sometimes literally created as a mirror image of the world.
Some of the earliest types of underworld mythology contain an underworld in which all people go to the same location upon dying. Early forms of underworld mythology, such as those found in ancient Mesopotamian and Egyptian texts, had a single underworld that all people would go to. The underworld of Japanese mythology is similarly inhabited and came to exist upon the death of one of the first gods. Similarly, the Greek underworld, at least initially, was such a place and was often referred to as Hades, though it eventually changed in myths to have different locations for different people.
There are other forms of underworld mythology in which there are multiple places for the dead, and where a person’s spirit went often depended on the life he or she lived. The Egyptian, Greek, and Roman underworlds became similar to these systems, wherein a person would be judged after death based on his or her deeds. Such systems often developed at least two different locations for the dead, one resembling an idyllic paradise and the other a place of punishment or penitence. These types of underworld mythology continue to influence both modern religious thought and creative depictions of fantastical worlds beyond life.