The great dungeon under Terrasquestone

In a prison without walls, without guards, and without law; what kind criminal would choose death over a prison such as this?

One destined to go to Hellgate Prison.

Dungeons, should make sense, in an ecological way. However, to have life, you need to have a physical place to use them. This expands upon the ecological dungeon, giving it a framework to exist in.

We have all seen articles on how Dungeons don't work. I've seen such articles before. But this time, an idea struck me: Why not do a dungeon that really works? Where creatures live their lives in harmony; just the right ecological way?