This story is a sequel to Best Hell Ever

Once upon a time, Twilight went to hell. It wasn’t that bad. It was pretty great, actually. It had a library! A big one. Like, bigger-than-the-universe big. But then Twilight went and got herself kicked out of hell, and now she’s depressed.

There’s only one logical solution: with Starlight’s reluctant help, Twilight is going to break into hell and invade its library. Oh, it’ll be tricky — trying to find one specific location in an infinite dimension tends to be a bit hard — but the infinite knowledge it’ll provide is too good to pass up. Twilight will find that library if it kills her (which, since this is hell, isn’t the worst thing ever in the grand scheme of things).

There is absolutely no way this can possibly go wrong.

Also known as, the Twilight.
I feel like this story doesn't need much of a description. After DJ Valkyri-3 I wanted to write more cutesy romance and see if I couldn't squirm my way back into ponified. Saw the picture and, well, this happened.
Also, I never really see Twilestia from Celestia's point of view. It's always form Twilight's or an omniscient view so I thought I'd try it out. Turns out it's really fun to write!
Enjoy!
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Added the sex tag for chapter 2 specifically, but unless insinuations without real descriptions and raunchiness with a dose of lewd iconography rubs you the wrong way then it's perfectly safe. It's still nowhere near needing the mature tag.

We all know the story of how the Princess’ young student and five friends defeated Nightmare Moon and brought Princess Luna back to our lands. But what if the tale were false? What if the young Twilight Sparkle on the event of her entrance exam had not been rescued by Princess Celestia, but instead lost her mind among the power of her youthful surge and had to be sent away, far away before she could destroy all of Canterlot with her newfound power. Now the feral unicorn prowling the Everfree Forest only vaguely remembers her past, slipping away from constant terrifying attempts to capture her.

And she is beginning to remember what true power felt like.

Editors include: Peter, Justin, Featherprop, Mitch H, and Bad Horse
Featured on Equestria Daily
Reviewed by Chris on One Man's Pony Ramblings and by Paul Asaran on his review blog
Now with a TV Tropes page

Physical books are available on Lulu.com
Monster in the Twilight (Paperback) 272 pages
Monster in the Twilight (Hardback)

There are many boundaries between an immortal princess and her student. Some are inevitably crossed when Spike accidentally sends a fantasy of Twilight’s to Princess Celestia.

Rated T for a little bit of mild spiciness, though there’s nothing explicit.

Takes place between season 2 and 3, with unicorn Twilight and alicorn Celestia. 

Won second place in the Twelfth Bimonthly Twilestia is Bestia contest. 

Featured on Equestria Daily

Cover Art by Akeahi on DeviantArt

Whenever Twilight’s favorite weather comes around, she and her wife drop everything to enjoy it with each other.

Cover art by Magnaluna
Winner of the twelfth bimonthly twilestia contest.

We all wear a mask called composure, beneath which hides a heart that twists with guilt and hidden feelings. Regal as she is, Princess Celestia is no exception. What might be revealed should circumstances cause this mask to slip - or break?

Set several years after the potential conclusion to the series.

This story is a sequel to Left Behind

After defeating the Broken Pony, Nightmare Moon is finally free to begin her plans to retake Equestria and restore it to its former glory. However, she is haunted by the ill portents she had been given and searches for signs of her sisters' fragments or the coming of any new alicorns.

On top of this, the king impedes the alicorn's work at every turn and tries to be rid of her just as frequently. So many things happening all at once and spiraling towards the doom the 'leftover tool' warned her about, but Nightmare Moon is determined. No creature will stop her goal, not even the dregs of Equestria's destroyers from so long ago.

Sequel: Left Behind: Sunny Disposition
Apparently it was scouted and is on EqD too

Nightmare Moon was meant to be released after a thousand years. A momentous occasion for her but terrifying for all the ponies on her day of freedom. She would get revenge on her sister and cover the world in darkness and shape everything to fit it.

That was the plan, at least. Instead, something went awry with the spell and she wasn't released when she was supposed to be. The mare-in-the-moon is brought into a world with stagnated technology, giant cities, and no sign of her sister or any of the other immortals. In fact, ponies don't seem terrified of her at all, and the stay within the core of her powers infused and changed the alicorn's body drastically.

The alicorn had no obstacles left! But...she was also a relic of the past. A past everyone seemed to have forgotten. A past she could no longer look upon.

Artwork by ElkaArt. Link in source.
Big thanks to Kryostase for helping spot errors I've missed.

Because sometimes, just because you're immortal doesn't make you invulnerable. Sometimes, the one you're more proud of than anything else is the one that respects you the most, and sometimes respect goes deeper than either of you had ever realised.

Additionally, because sometimes an author wants to try and write something that doesn't end in horse sex, but instead adorable hugging and stuff. If this doesn't work out I'll probably go on and add some horse sex later, because people always like to see that, but I hope people enjoy it. My first foray into a full sized shipping fic, so please tell me what I screwed up.

EDIT: Updated with grammar improvements/education courtesy of the incredibly helpful kits.

Twilight Sparkle wakes from a coma after being cursed by a stallion she doesn't remember ever meeting. Princess Celestia and Spike have been taking care of her while she was sleeping. But something is wrong, and Twilight’s memories don’t match up with anypony else's.

This is an AU story of my own twisted imagination. Set after “Games Ponies Play” but before “Magical Mystery Cure” timeline wise (sort of, you'll see). So no Alicorn Twilight here. Tagged Twilight and Celestia as they are the main characters, but other characters do appear in the story.

Descriptions are hard. Big thanks to my Pre-Readers Nakrab and Dumbgamer99!

-- Soft Story