OK, first of all hello!
I've been lurking in these forums for quite some time now and have always found great information and inspiration. So, now I have really stuck at the development of my campaign setting and I could use some help.
My players are going to visit a very dark place in the world, where in the past several important event unfolded. The history of the place is crucial to the past of some PCs and also to the adventure (and I also like this place a lot) so I want the history to be based on a solid base.
Some time in the past, the Princess of the region was called by the Shadow and travelled far away. And when she came back she came claim the world for the Shadow. War ensued, etc, etc. At one point she completed a ritual and all the stars from the sky vanished. Note, that star in the sky=soul of a dead. The dead were awake and for ? years the spirits of the dead could not be put to rest. More war, more chaos, until some heroes with an artifact managed to defeat her (actually her brother!).
After that, a special paladin order was created which built castles/temples around this dark realm to keep the evil inside. This is where my players are going!

So, I was thinking these events were dramatic and affected most part of the known world. Two questions: how long could the age of starless sky last? 5? 10? 20 years? I was thinking around 5-10 years. I mean I want it to be dramatic but I don't want it to leave the world in total ruin. Then how long since that time are the players coming in? 200? 300? 500? years? I was thinking about 250-300 years. Long enough to recover, but not that long in order to stop being a threat.
I know all these might sound like a complete crap. But I really like the story and I'd like to figure out the numbers to make it work and seem plausible.
Thanks for your time guys!