Princess Twilight Sparkle finds herself caught in a conflict as old as Equestria itself when a twisted creature, birthed of the cruelty of the ancient unicorn empire, returns from banishment seeking retribution. But Princess Celestia is strangely unforthcoming about this new threat and its brutal magical powers, even as she enlists Twilight's help once again and sends Rarity and Applejack on a long and dangerous journey north. Meanwhile, the gentleponies of the Royal Court and the National Assembly are becoming ever more troublesome as they see Celestia's grip on Equestria weaken. And what secrets still lie hidden in that vestige of empire—Somn, the city on the edge of the world?

Note
This story was started a long time ago, and diverges from canon in between seasons 3 and 4, shortly after Twilight became a princess.