Long ago, following an age of gradual bitterness and hatred, the map of Equestria was divided in two parts: Solar Equestria, ruled by the Princess of the Sun; Lunar Equestria, ruled by the Princess of the Moon. Rarity Belle, living in Lunar Equestria, was but an aspiring seamstress who unexpectedly got summoned to the Royal Palace of Princess Luna --- all in a hunt for a priceless, mystic crystal near the borders of the rival country.
Things could only go well from there.