I came up with my own setting a couple years back called Acerbitor, which was a combo of Acerbus and Nitor, the latin words for Light and Dark. It was a world that was once technologically advanced, but a mad wizard called down a meteor which screwed up the orbit of the planet causing one side to constantly face the sun, the other to be constantly dark. This also caused the collapse of the technological societies and pretty much reset everything to medieval. 200 years later, the old societies are being excavated and slowly rebuilt, but only a few nations have the knowledge to build their own mechanical stuff, the rest can only excavate it and restore it.
I thought it was neat. One thing we did was only have 3 gods. Dark, Light, and Time, all of which were neutral.