Mystara: The Known World

From the Introduction:

So you're new to the MYSTARA campaign settings... or at least you think you are. If you've come to D&D® fairly recently, perhaps with the release of the 3rd Edition rules or maybe even during the 1990's, MYSTARA quite probably is a whole new realm for you and your gaming buddies to explore. However, if you're an old-time D&D player but don't think you've ever encountered MYSTARA before; you may be surprised by some of the information that follows.

Here you'll find a brief overview of the origin of MYSTARA and a discussion of the things that really define the campaign and give it the flavor and atmosphere we love and hope you'll enjoy too.