A month ago, Paul chimed in on “20 Dungeon Ideas to Explore” and suggested that I work up some sort of abandoned, underground city that was built by the dwarves and vacated when they dug just a little too deep and found something too vile to deal with… So I thought it was high time to explore that idea a bit.
What I hit upon was that a group of deep dwarves (perhaps Duergar, perhaps not) was expanding their domain, as dwarves are wont to do, and moved a keystone preventing the release of something in the dark…
Eons ago when the planes were new and rubbed elbows more frequently, there was a plane of complete darkness which sought to consume the light. This race of creatures fed on actual light and would seek out any sources… ultraviolet through infrared was a smorgasbord of taste sensations. There may have been suns there at one point, but these creatures devoured them from within.
They were threatening to invade the prime material plane when a tectonic shift moved to block their entry into the world. Over time they devoured all the light in their own plane and they began to die off until only the strong were left. That was the end of it, right?
Obviously not. But that brings us to the time of this group of dwarves accidentally broke loose the key stone, releasing a few of these creatures of darkness into the bowels of their subterranean world. Down there in the deep, magma flowed from time to time. The darklings consumed the dwarves, as creatures of light, and then sought out more tasty morsels such as lava flows. When more dwarves discovered these creatures devouring their world a light source at a time, they did everything they could to stop them but nothing worked.
Eventually they made a deal with some of the devils of the Nine Hells to seal the creatures in the darkness they call home. A series of hellish runes were laid, lives were sacrificed, and an entire portion of the city was sealed away. There was nothing left to do but acknowledge their new pacts with their new masters and abandon the deep city to the dark.
It is thought that should any of the runes be damaged or destroyed, even the devils of the Nine Hells may not be able to stop them. But in recent years, there have been rumors from the deep that even the svirfneblin have begun to leave their homes. Scholars believe that the gnomes are safe, as they have never even seen starlight, let alone the light of the sun – so they are as much creatures of the dark as these darklings are.
Should the darkness rise from the Deep City, there is little hope for the world…
Sounds like a great campaign for the PCs to enter the Underdark and try to find the leak and stop these creatures… but they may have to get some powerful allies to actually affect the course of things. The darklings have been wanting into this world for eons… they’re hungry. And they’re coming.