The Underworld was also known as the Dark Territory.
In the legacy of the World Tree that Eve had obtained, there wasn't much description about the Underworld. She only knew that the history of the Underworld was not shorter than that of the surface world, and perhaps even longer.
It was said that at the very beginning, several ancient gods who were defeated during the Creation Era had delved deep underground, creating this dark world.
However, over time, these ancient gods fell one after another or degenerated into evil gods. The Underworld was gradually occupied by newly-born intelligent beings and others coming from the surface world, bringing with them the faith of True Gods.
Unlike the surface world, where kingdoms had formed, social order had been established, and wars had significantly decreased overall, the Underworld was filled with bloodshed and chaos.
Wars, conquests, declines, and collapses formed a similar cycle among the various realms of the Dark Territory.
