Fifty years past, there was a place where not even the great Sun-Goddess Celestia had power. In a place where only earth ponies and unicorns lived, the great evils of uncontrolled scientific inquiry were proven, and the dangers of ambition were made clear for all there to see.
This is the story of a pony who stumbled across the great city of Euphoria and became embroiled in the greatest power struggle Equestria never saw.

This isn't a pure crossover.