Great Derue Dungeon.

The Great Derue Dungeon, formerly known as the HMS (Hybrid Mountain Shelter), is a mountain inhabited by powerful monsters.

Before the World Energy Reset.
The HMS was a mountain re-constructed to be a shelter for humans.

It's made to protect from huge natural disasters and wars.

The HMS was constructed to be a living space that can sustain itself for humans incase of World Wide emergencies.

The HMS was powered by a large source of CG Energy.

It has an artificial sun and weather so they'd be able to live in the HMS for a long time.

The World Energy Reset.
The HMS did not have a CG Barrier, like Fleole, and contained a large amount of CG Energy.

The Reset caused the Humans to be combined and turned into monsters or became demons, that were killed by the monsters.

Over the Hundreds of years the monsters expanded to every Layer of the HMS.

After the World Energy Reset.
Some CG Energy powered machines were able to survive inside the HMS and adjusted to the envoironment, making them act a monster-like behaviour.

Years later adventurers started to explore the Mountain and named it the Great Derue Dungeon as it contained a lot of layers and monsters.

The Dungeon was popular by Adventurers because of it's large amount of monsters, making it a place for gathering rare materials and to sharpen their skills.

Top: The Great Derue Blizzards.
The Great Derue Blizzards is an area with extremely low temperature and inhabited by Ice-type Monsters.

Upper Dark Transitional Layer.
The Upper Dark Transitional Layer is an area inhabited by Dark-Type Monsters.

This Layer is below the Great Derue Blizzards.

It is a massive cave with no light sources.

It blocks the Artificial Sun from shining there.

Middle: The Great Derue Forest.
The Great Derue Forest is a neutral envoirenment with a variety of monsters with multiple types.

It is a labyrinth-like forest with massive trees and many monsters.

It is the direct entry and exit from the Great Derue Dungeon.

Lower Light Transitional Layer:
The Lower Light Transitional Layer is an area inhabited by Light-Type Monsters.

This Layer is below the Great Derue Forest.

It is a massive cave with many lights.

The sun enhances the brightness of the caves.

Bottom: Great Derue Volcanics.
The Great Derue Volcanics is a layer inhabited by Fire-Type monsters.

It has extremely high temperatures and lava seas.

Fallen and abandoned machines from before the Reset are still there.

There are monsters that are able to swim in lava.