This story is a sequel to The Fiend that heralds Dark Skies
(This story is the sequel to The Fiend that heralds Dark Skies, which itself is a sequel to The Mare that eats The Monsters. Reading the first 2 stories is STRONGLY recomended to understand anything in this one.)
Twenty years ago, Princesses Luna and Twilight Sparkle were turned to stone and hidden away from Equestria by an old monster, once a pony, named Luminous Horizon. His intent was to release them when Equestria was nothing more than dust and rubble as retribution for the pains he suffered at Luna's hooves. They will be released before then, however, thanks to the efforts of Palmwood, Wonderboom and Moonrise Drifter. Together, they intend to set the imprisoned princesses free and bring an end to the unyielding darkness over the world.
This third and final story in the series will see the thousand year conflict end; for better or for worse.