Twilight isn't having a very good day. An experimental spell blew up in her face, an army of changelings is attacking Canterlot, and she just died. Yet somehow, it looks like it's going to keep going downhill from here.

Given the chance to correct what's gone wrong, Twilight swears she's going to fix all this even if it kills her. Which it will. Frequently.

Cover art by Pixel Prism
Spanish Translation
Series TV Tropes page

Sweetie Belle gets stuck in a time loop.

Traducción Española: https://www.deviantart.com/spaniard-kiwi/art/Un-poco-circular-1-4-990271915

Proofread by many people such as: 0_0, refferee, Leonzilla, crooked, TheGreatEater, and other people I may have missed.

Twilight Sparkle broke time when she got her cutie mark. Now Twilight and Sparkle are sisters from another time. Twilight is hailed as the potentially greatest light magician of all time, and already has a reputation as a hero by the time she goes to Ponyville. This isn't her story, not primarily.

Sparkle is an orphan - her dark magic killed her parents. She lives with her brother in Canterlot's industrial sector because they can't afford anything better. She can't leave either. She's a natural dark mage; while Sparkle won't go mad like Sombra, her reputation is hardly any better. Worse, the law doesn't see her as a good pony.

The fact that the dead don't stay dead around her, or that Thorn - Spike's double - is an undead, soul-eating abomination, are other matters altogether.

(Also has some Slice-of-Life, but fimfiction tags won't let me put it with Adventure.)

Has an ask blog to go with it: Ask Sparkle and Thorn.
Also has a TvTropes page: Split Second Tropes.

Featured on EQD.

Cover art by Swirling Line.

On a dark night filled with even darker magics, an insane cult attempts to give Nightmare Moon a body and life of her own, utterly separate from Princess Luna. But, when the spell is interrupted by Celestia, something unexpected is created.

Now, a little black alicorn filly named Nyx finds herself living under the care of Twilight Sparkle, only to be haunted by memories and emotions from her past. Is she Nightmare Moon reborn or is she simply a doppelganger with a soul and mind of her own? Can Twilight Sparkle protect Nyx from those who refuse to see past her dragon eyes and black coat?

Or, will Nyx be forced to inherit the sins that may not even be hers and become the greatest evil Equestria has ever known?

I woke up in the hospital. I don’t recall how I got here. I don’t recognize the mare who says she’s family. I don’t even remember my own name.

So what kind of pony will I become?

"My name is Lyra Heartstrings, and you will not remember me. You won't even remember this conversation. Just like with everypony else I've ever met, everything I do or say will be forgotten. Every letter I've written will appear blank; every piece of evidence I've left behind will end up missing. I'm stuck here in Ponyville because of the same curse that has made me so forgettable. Still, that doesn't stop me from doing the one thing that I love: making music. If my melodies find their way into your heart, then there is still hope for me. If I can't prove that I exist, I can at least prove that my love for each and every one of you exists. Please, listen to my story, my symphony, for it is me."

Cover pic by Spotlight: askspotlight.tumblr.com