This is a type of dungeon mostly grows in the ground. It normally has a hidden entrance. They grow mostly in out-of-the-way places in caves or entrances to the underworld. They grow from a seed of chaos that magically appears in locations where no creatures with intelligence or wisdom have been for a while. The closest creature that lives in the area is lured to become the chaos master of the new dungeon. When they become the chaos master, they gain levels of intelligence and lose any levels of wisdom they might have had. They create the items and other creatures in the dungeon from their flights of fancy. Each year that a dungeon is undefeated the dungeon grows a level deeper in the earth. One defeats a dungeon by killing the chaos master.
Creatures in a chaos dungeon do not normally exit through the main entrance, but they may spill out into the area if they become overpopulated. This causes a horde of monsters that may attack civilized areas. This is how some dungeons are found as they might not be seen until a horde must be defeated.
The negative pressure of magic can be found around a chaos dungeon. The reason for this is the magic in the area is used to make and enhance the dungeon. The longer the dungeon survives the larger the area that is affected. The horde of monsters or the negative magic pressure is normally how a chaos dungeon is known to exist.
Sometimes when a chaos dungeon is expanding it may break into a cave in the underworld. This creates an additional entrance and may allow creatures in the dungeon to come and go into other areas as they please.
If a chaos dungeon is not collapsed after it is defeated other creatures may use what is left as a lair or entrance to the underworld.