A thousand years after the Princesses disappeared from Equestria, Twilight Sparkle meets a lost Cloudsdale scout named Rainbow Dash. Together they look for a way to end the thousand-year night and dispel the darkness that has spread across Equestria.

Edited by Pascoite
Contains fairly mild grim-dark. Inspiration taken from the Dark Souls games, but it's not strictly a crossover.
Chapters titled "Arc #: Chapter Name" are part of the main story. Chapters titled "Character: Chapter Name" are one-shots about other characters, set in the same world, and aren't necessary in order to follow the main story.

Everyone knows the story of Hearth's Warming Eve. Everyone knows how six ponies brought the three tribes together and banished winter with the magic of friendship. But what if fear and hate had won instead, and created a society where winter is eight months of the year and earth ponies are little better than slaves. Millennia later, a dark lord plans to use that hate to power a foul magic. Can six new ponies, brought together by chance, find a way to end the winter, or will they be just a footnote to the end of the world?

This story is a sequel to Luna's Protégé

'Or through Midnight's Radiance, the Sun extracts obedience.'

Things are looking up for Sunset Shimmer.
She's been a proud student of Princess Luna for over twelve years, has the best friends a pony could ask for, a young dragon she cares for dearly, and ambitions on the cusp of completion.
And even better, it looks like everypony will be spending the Winter Solstice together! Assuming of course, that Celestia's return doesn't end up ruining everything...

Distant sequel to Luna's Protégé
Thanks to Cloureed again for the cover!
Set in the Trio-verse.

Twilight Sparkle, a ward of the crown ever since she accidentally turned her parents into plants, is dispatched by Queen Celestia to the small hamlet of Ponyville; the Unicorn has expressed fear that an eldritch Alicorn of the past will arise there. And when Twilight Sparkle fails to defeat the fiendish NightMare Moon in the two Queens' former palace of Concordia Arbos, the planet is plunged into night on one side and day on the other. With only shards of rock to her name and a band of ponies at her side, she sallies forth to bring back the Sun. She will traverse field and mountain, desert and labyrinth if she needs to. Will she be able to solve the mystery of the Elements of Harmony? Who was NightMare Moon, and what evils come to Equestria apart from her everlasting night? And why does Queen Celestia believe that making friends takes priority over everything else for Twilight...?

Can be found on TV Tropes.
Has a YouTube reading by our own Alchemystudent.

The Elements of Friendship, Book I: Harmony
The Elements of Friendship, Book IS [interlude one-point-five]: Bonds
The Elements of Friendship, Book II: Chaoskampf
The Elements of Friendship, Book IIS [interlude two-point-five]
The Elements of Friendship, Book III
The Elements of Friendship, Book IIIS [interlude three-point-five]
The Elements of Friendship, Book IIII

Equestria: The shining beacon of peace and harmony in a world torn by war. The citizens are safe and secure within the borders.

However, a darkness is coming. Sunset Shimmer, daughter of Celestia, fears the return of the goddess of the night herself: Nightmare Moon. A mare who wishes nothing more than the destruction of everything good. Sunset will do anything to stop her.....
...Even if that means hanging out with other ponies.
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I know you all have seen your fair shair of Alt-universes, starring a different main six. I know this, but I couldn't get the thought of trying my own hand in the concept.
{I'm also hoping I live up to the standard set by my predecessors.}
I shall call my 'verse, "The Shimmerverse"....Genius!

(Edited by The Albinocorn. Thanks for the assistance.)
Coverart by F-NAR
I hope I did well and you enjoy it.
Please leave a comment.

A flip of a coin. A twist of fate.

Twilight Sparkle, younger sister of Princess Celestia's personal student, Shining Armor, grew up listening to her brother's bygone dreams of joining the elite of the elite: The Royal Guard.

Now, fresh out of the Academy, this young mare is ready to prove herself equal to the deeds of the great soldiers she read about as a filly. Too bad the princess she ends up protecting isn't Celestia.

This is a parody of avatar the last airbender, using ponies! Read as the avatar, Twilight Sparkle, travels on a journey to stop the water nation's war against the world. Constantly pursued by Nightmare Moon's daughter as well as the general of Water Nation will she be able to take and complete her first step towards becoming the avatar?
Special thanks to Duelist925 and Angel_Bunny for editing the chapters for me
Please enjoy!

Full collection:
Avatar the Last Alicorn:
Book 1.
Book 2.
Book 3.
Book 4.

Legend of Diamond Tiara:
Book 1.
Book 2.
Book 3.
Book 4.

Disclaimer: "Avatar: the Last Airbender" and all associated characters, storylines, and materials belong to Nickelodeon and were created by Bryan Konietzko and Michael Dante DiMartino.
My little pony: Friendship is magic and all associated characters, storylines, and materials belong to Hasbro, and was made incredibly awesome by Lauren Faust.

One thousand years ago, Celestia failed to reach out to her sister and save her from the darkness that consumed her. In her sorrow, she was forced to seal her within the Moon.

Five years ago, Sunset Shimmer, Celestia's personal student, also turned twords a darker path. Celestia once again sought to save somepony she cared about from falling onto a dark path. This time, she succeeded...

The first story of the Sunsetverse, join Sunset Shimmer and Twilight Sparkle, Celestia's personal students, as they are sent to Ponyville to oversee the Summer Sun Celebration. Oh, and make some friends. Sunset's not so sure how that counts as a job, but it would probably be a good thing for Twilight. Poor girl's obsessed with some Mare in the Moon legend she read. A few days out of the library and interacting with other ponies would only be a good thing for her, right? After all, there is no way Nightmare Moon is real.

*Edit*-10-6-2014 : *spittake* I'm a featured story? What? What? What? I don't even, how? ...I need to lay down for a bit. Um, thank you all my viewers who made this possible, and thanks to the staff for enjoying my work enough to feature it. I will strive to do even better in the future, and once again thank you for all of your support.

After reading a story to his little sister, Princess Celestia's student Shining Armor believes that the legendary Mare in The Moon is about to return. After disregarding his warning, the princess sends her student to a small town called Ponyville to look over preparations for The Summer Sun Celebration. There, he, his sister Twilight Sparkle, and young dragon companion Spike, meet some strange mares and odd fillies. How will he survive a town full of crazy ponies? And what will he do when it turns out he was right?

The story is inspired by the Twiley chapter of Crisis of Infinite Twilights written by Defender2222.

Now the first in what I'm calling The Shiny-verse

When a freak and powerful storm rolls in from the Everfree, strange events are set in motion. Reports of bizarre creatures, odd ponies and wild magic abound.

The Bearers of the Elements of Harmony must face down their enemies, fight for their world and face their fears. Some of the bearers must face even more than that, and face them alone. Read now as ancient secrets are unveiled, powers thought lost are unearthed and powerful despots seek to rule with an iron hoof.