500 years ago, the Pegasai of Cloudsdale betrayed Equestria to a cataclysmic storm called the Reckoning. Now, the storm has begun to fade, and Cloudsdale is ready to retake the world they wiped clean.

But the world they find is not as clean as they had hoped. The descendants of survivors guided to safety by Luna have had 500 years to plan their revenge, and now they've come...for Retribution.