The fourth level of the Hero Domain, the Dwarf World.
This was an underground world with rock barriers everywhere. In this underground world, there were countless crisscrossing tunnels, deep and dark rock caves, bottomless caves, and so on. It was a rare residence for intelligent creatures.
The duergar cave was one of them.
The size of the duergar's cave was equivalent to the size of several ordinary main material worlds combined. It was the largest gathering place for the duergar race in the dwarven world. There were countless duergar living there. Whether it was a small clan, a grand fortress, a fortress, an empire, and so on, they could all be found in the duergar's cave.
This cave was sealed off, and there was no light at all. For most intelligent creatures, including many dwarves, it was an uninhabitable environment.
However, the gray dwarves were cave dwellers and loved the dark underground. This was their paradise.