Its a RPG cliche to have huge ruins and caverns filled with monsters and treasure chests. Of course, it is perfectly logical to have these things in a video game; you know it's not real, so you don't question it. Of course, in the world of Symptoms, dungeons with monsters and treasure are a complete reality. So, why are there places like that, and how did they get there?
It is more of a theory that Mainland scholars created to explain Dungeons. Basically, that they were once sacred places, used to worship the gods and in turn were blessed. After the Great War, however, when belief in the gods wavered, the blessings on these sacred lands were dissolved, and the once sacred lands were cursed and thrown into chaos. Monsters overran the areas and attacked any who came near. What was once offerings to the gods became scattered about the once sacred areas; unique items all boxed up and hidden away. Giant gates were created to keep people out, but the keys were always hidden in obvious places just in case one had to get through. Over the years, adventurers entered these now cursed and ravanged lands to prove their strength and obtain the items that were hidden away.
The name "Dungeons" came from the resemblance to a castle's dungeon. Many of the areas with very strong monsters were covered in the bones of the adventurers that could not survive. Some of the "Dungeons" were buildings built to the gods out of stone, like a castle dungeon, while others were natural places like caverns and deep woods. Soon the name came to apply to all of these cursed and dangerous places. In later years, dungeons popped up for other reasons. New areas became overrun with monsters even though they were not these cursed lands. These giant monster nests were also called dungeons, for most people forgot the actual reason dungeons appeared.
One thing the Guild on the Mainland seems to be doing constantly is going into dungeons. They have just become a normal part of life to the inhabitants, and many materials needed for living come from the dungeons or the monsters within them. The Guild constantly goes out and gathers supplies that the citizens request, or map out and explore new hostile areas.
