Discord had one last trick up his sleeve to play before being locked up again: he's turned Equestria's timeless protector into its most dangerous threat. The kindhearted princess that ponies loved and adored is gone, replaced by an alicorn of iron and blood that forged Equestria out of the fires of pre-history.

Can Twilight Sparkle survive being the student of a pony who never had need of the magic of friendship or will she be forced to sit on the sidelines as Equestria irrevocably changes around her?

There's something strange and unnatural living in Bon-Bon's house.

Something other than Lyra.

[Complete] Celestia awakens to see an empty world, white sandstone stretching the horizon. She wanders the world as she builds it from her imagination, filling it with life, but as time passes, the world that she created begins to seem like little more than a lucid dream, conjured from the dust.

There was only one explanation. For all of it. All of the strange, erratic behavior. Her irrational fear of the sun. Her nocturnal habits of locking herself in in the dark and closing all the blinds. Wearing her sunglasses everywhere, even inside! It was time to invest in some silver, garlic, and a wooden stake.

When facing Twilight Sparkle, Nightmare Moon was given a choice: redemption or revenge. What if she had chosen the latter? A grim fate awaits Equestria, but in a time of greater strife and conflict, Discord's return is accelerated. While he expected to bring chaos, he did not anticipate that he would end the Longest Night and bring hope and joy back to the land.

Discord struggles to reconcile his nature with his desire for admiration. While Twilight's friends strive to carve a new life in the ever-shifting Equestria, she searches for Celestia, the only one who can bring harmony back to her lands. But Nightmare Moon also seeks her sister in a desperate attempt to find her place in the world. New dangers lurk in the wild and more threaten to fall over Equestria. Nightmare Moon's decision broke the balance of the world. Will Equestria ever turn to peace, or will the spiral of chaos and destruction be the end of everything?

(An alternate history, this story takes the universe established by the canon and explores one possible outcome if Princess Luna had not been redeemed.)

Comments contain huge spoilers. Walk softly.

Special thanks to my pre-readers, MmmandarinOrange and DarkmatterButterflies for keeping my head on, taking the journey of the story, and making it so much better than it would have been if I wrote it alone.

Pinkie Pie is hiding something and her two friends Rainbow Dash and Twilight Sparkle know it. To what length will they go to find the truth, and how much danger are they willing to put themselves in?

Twilight becomes alicorn of the stars. This is sort of a problem, because Luna kind of already was alicorn of the stars. Oops!

TV Tropes

For almost a thousand years, the immortal Nightmare Moon has reigned over Equestria as Empress. To the average pony, Nightmare Moon is an overarching enigma whose rule is absolute and whose wrath is terrible. But to Twilight Sparkle, who as an orphan has never known her parents, the Empress is something else entirely. When the young unicorn is brought under the royal wing as an apprentice, she learns a great deal more about the supposed tyrant than she ever knew. But as Twilight is introduced to life with her new mentor, she is thrust into a world of political intrigue, conspiracies and secrets. Secrets that were never meant to be revealed. As allies and enemies plot against the very peace of the nation, will Twilight fall prey to the perils of her new position? Or will she prosper and find in Nightmare Moon the mother she never had?

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My eternal gratitude to my editor, LordOfTheWrongs, without whom Night's Favoured Child would not be the story it is today.

Now with added TVtropes!

Celestia leaves to deal with a foreign crisis, giving her sister a chance to rule alone and become more attached to the modern world. She calls on Twilight Sparkle to advise Luna, hoping her student will be able to draw Luna out of her shell. With two major threats to Equestria already defeated in the past year, it seems like the perfect time to let Luna gain some confidence and experience in the modern world. After all, what are the chances of a third disaster occurring?

Now comes with complimentary tropes.

Humans.

Truth or myth? Ancient lost civilization or just an old pony's tale?

No pony has ever seen one, and most haven't even heard of them. But Lyra knows that these wonderful creatures are more than just old legends, and she's going to find out... and possibly drive her roommate insane in the process.