The Frozen North has been a constant in Equestria for over a thousand years, a forbidding wasteland occupied by a constant blizzard no life can survive in. Long ago, it was not so. The Crystal Empire was a prosperous realm ruled by a wise and powerful sorcerer-emperor, that lived for many years in peace with the Equestrian diarchy to the south. This is the tale of the end of that empire, the war that consolidated the power of the Two Queens, and the spark that would ignite Nightmare Moon's Rebellion. This is the tale of the Crystal Empire and the King in the North, a king that was vanquished, but swore one day to return.
In the same universe as Camaraderie is Sorcery, to be read between the second and third seasons (after Chapter 2:27.3).
Heavy inspiration for story and structure taken from The L-Train and the Royal Canterlot Symphonic Metal Orchestra's Fall of an Empire.