When one spoke of a dungeon, the common image that came to mind was an isolated rupture in space itself—
a jagged crack in reality that served as a gateway to a separate, hostile dimension.
These were known as Crack Dungeons, and they were fundamentally different from their other counterparts.
Unlike Plain Dungeons, which naturally formed within the world and followed predictable internal rules, or Bounded Field Dungeons, which were sealed within artificial barriers and strictly regulated, crack dungeons were unstable by nature.
They were wounds in the world.
Unpredictable. Violent.
Most dungeon outbreaks originated from these cracks.
As mana accumulated within the inner domain, pressure would build relentlessly.
When the internal balance collapsed—or when the mana density exceeded what the surrounding space could contain—the dungeon would rupture further, spewing monsters into the outside world like a flood bursting through a dam.
Entire cities had fallen to such events.
