In the central continent, there is an ancient quarry.
The pit is gigantic, over a thousand meters deep and spans several kilometers.
It was said that something ominous was unearthed from the pit, leading to its abandonment before being converted into a Heavenly Prison.
The mine's top and bottom are carved with countless tunnels.
There are over a thousand in total, resembling a building, layered and varied in depth.
Some mine shafts extend over hundreds of thousands of meters, while others are over a thousand meters long.
Cages are excavated on both sides of these shafts.
The doors are forged from the mine's iron ore, a bluish hue of iron said to be unbreakable even by an Immortal King Sword.
