What could have happened if Nightmare Moon had won over Twilight Sparkle and her friends? The tome Princess Celestia gives Twilight explains what she saw while using a spell. It shows a new threat to Equestria, as well, and Princess Celestia said this story has no happy ending.
Story Two of the Haven Trilogy, a partial sequel to Solar Flare concerning the second tome Twilight Sparkle received. I don't feel this is close to the best I could do, considering that when this was written, I was suffering from an immense case of Writer's Block.
http://www.equestriadaily.com/2011/06/story-solar-flare.html
SOON TO BE REWRITTEN
Chapters (1)
Great story, I really enjoyed it.
286300
It's being rewritten soon enough. When I first wrote it, I was suffering from immense writer's block, enough I actually had to bring one of my editors in to write it. It became rushed and ended up suffering because of it. Nice to see the editor of AtFN here reading this.
Wait, so has this been rewritten yet? Or is it still the version you felt was rushed?
380116
This is the previous version. It has not yet been rewritten.
989155
Fixed. However, the Everypony tag came about after I uploaded these stories.
990742
It was meant to be many times longer than it was. But immense writer's block coupled with the want to finally get it finished led to it being that length.
This reminds me very, very strongly of the story "After That Fateful Night". Same general idea: Nightmare Moon wins and takes Twilight as her pet and gradually sheds the heartlessly evil persona. Personally, I've always thought that this would be inevitable; Nightmare is, after all, Luna and the difference between the two would logically dissolve when the bitterness and pain that made Nightmare faded.
Which, incidentally, gives me an idea...
1212158
It's the other way around. After That Fateful Night was written months after I released this on Equestria Daily. After finding ATFN, I immediately noticed numerous parallels between my fic and that one, as well as parallels between what my fic was supposed to be. Back before I started writing WCHB, I was very vocal on a chat and a forum about what was going to happen in it. I called shenanigans and plagiarism. The author denied it vehemently, then had himself and his editor come in just to One star my story on EQD and thumb down it on here. That's where the two thumbs down came from. The plagiarist.
When I started writing it, however, I was suffering from immense writer's block. Originally, WCHB was supposed to be a several chapter fic stretching from NMM's takeover, her takeover of Canterlot and eventually Equestria, Applejack starting a rebellion, a war starting from shadowy creatures (Though in the rewrite, I'm changing it to the Changelings because I never could decide what I wanted the creatures to be.) And then an eventual peace being brokered before Erebus' arrival.
1216135 I mean no offense, Dragryphon, but what your work reminds me of is a matter of personal perspective, not fact. I didn't say that you seem to have gotten your idea from AFTN, which would have been incorrect (as you so articulately explained), but that your shorter, writer-blocked work reminds me of a relatively massive work that I've read and enjoyed. When you dynamite your mental logjam and expand this into a work of greater length, I'll enjoy seeing what comes of it but at this point, I have no way of knowing if your story will be as richly detailed as the doppelganger of your concept because you haven't written it.
As to your shadowy creatures, there's no need to give up and make them into changelings! As Erebus has so adroitly demonstrated, there's lots of evil things festering in the shadows that are completely alien to the ordinary canon of the show. I think it's absolutely smashing, though, that so many authors have randomly collectively concluded that the Greek underworld would be the best analogue for how the MLPFIM heaven/hell dynamic works.
Speaking of such... furies would be an awesome baddie army. Just saying.