Introduction
 
The surface isn't safe anymore.
In the ruined depths of Canterlot, a team of brave salvagers discover six mares, long forgotten but miraculously preserved. Though these mares cannot remember what happened to their world, they possess powerful magic that hasn't been seen for centuries.
Now the Elements of Harmony are thrust headlong into a world beyond recognition. Twilight and her friends must dive into the sunken remains of history to determine what happened, but Equestria isn't the harmonious land it once was. Before they can focus wholly on the past, they may first have to survive the present.
It isn't going to be easy.