Sometimes when you lay in bed, just as you reach that cusp of sleep, something happens that jars you awake. This time it wasnt a sense of falling - instead, it took a small dungeon area I'm working on and tossed it on its side.
I've got two undead races, each mostly on it's own level. They are cursed with a sort of Raganarok effect - perpetual war where each side's fallen arise again at the start of the new day. When not at war, they are desperately mining for a magical gem that can release them form this curse - but each morning, their mining efforts are also reset.
So, the idea is now, to determine what state the "dungeon" is in when the PCs arrive. Is one undead race or the other waging war, thereby leaving one level mostly underpopulated and the other in a chaotic state of battle? Are they peacefully mining and apt to ignore PCs that are leaving them alone? Can the status change in the middle of the PCs exploration? Can the PCs actions tip the tide of battle and allow the winning side the time to finally recover the gem they are looking for?
Probably won't play out the same for any two groups. Is that good or bad? Damned if I know...
I need to write this out in a coherent fashion ;)