0X.08: Underrealm Depths
Form: Extensive networks of caverns and tunnels leader ever deeper into the earth.
At First Glance: Beyond the Bastion (0X.05) the caverns and tunnels of the underrealm become ever more complex and unmappable. It seems like one could travel for miles, going ever deeper, and never discover anything with certain meaning.
On Closer Inspection: The farther the characters travel, the more certain they are that the dwarven Bastion was there to block the lower depths, not serve as a gateway to it.
Secrets: Those cold, dark, lonely caverns are inhospitable and dangerous. Every four hours the characters spend exploring, there is a chance of a deep encounter. The check gets progressively worse for each four hours spent exploring and eventually the worst will happen.
Connections: If followed forever, these caverns will eventually lead to the Netherdeeps, a hellish subterranean realm beyond the scope of this adventure.