This is an idea that wouldn't leave my head, inspired by Fairy Slayer's "Mommy Nearest," Aldea Donder's "Alicorn," SoundofRainfall's "Play" and RainbowDoubleDash's "Lunaverse"

Alternate Universe: Instead of Twilight Sparkle, Princess Celestia made Rainbow Dash her personal student instead! Follow her through the events of the 1,000th Summer Sun Celebration. A reimagining of "Friendship is Magic"

The sequel to League of Discord. Twilight Sparkle and her friends have successfully returned the six champions to Runeterra, but find themselves dragged along with them. They must now find a way home, despite having no help from an apathetic League, and having yet another pair of ambitious and sinister eyes watching their every move.

Inspired by the heroics of the mysterious mare known as the Stable Dweller, Silver Storm, a guard of the town of Marefort, decides to go on a daring mission to rescue her captured brother. Of course things rarely go as planned and her attempts at heroism drags her into a tangled web of plots and conspiracies as warring factions vie for control over the last great city: Dise.

Spanish Version translated by Spaniard-Kiwi: https://www.deviantart.com/spaniard-kiwi/art/Fallout-Ecuestria-Heroes-996263393

This story is a sequel to Upheaval: Breaking Point

Following the events of Breaking Point, Twilight Sparkle and her friends discover that Equestria's demise may not come from an enemy invasion, but from within. The Barrier Lands and the Heartland begin the slow and uneasy process of reuniting into a single Equestria, but this long-delayed joining is already in danger at its conception.

With Celestia's power in her grasp and her agents by her side, the wheels of Black Rose's plans for Equestria's future continue to turn. However, her brazen gamble has done more than just bring down a centuries-old barrier. Ancient powers begin to stir: the remnants of a dark period in Equestria's history, the immortal inhabitants of Celestia's homeworld, and a rising tide of darkness coming ever closer.

Equestria is a land of magic and harmony, a peaceful realm ruled by immortal and benevolent monarchs. At what cost is this possible?

Following the discovery of a strange and powerful device, Twilight Sparkle is whisked away to the edges of a land she thought she knew so well. Here, surrounded by ponies whose very existences have been kept secret, she must contend with vicious enemies, hostile allies, and the truth.

Chapters 1-16 edited by KiltedKey

The following transcripts are of a journal found in Ponyville on April 16th of this year. The last recorded contact with the town had been 3 days prior, on the 13th, when a team under orders from Princess Celestia was sent to look into several missing pony reports in the area. When another group of investigators were sent on the 16th, the town was found deserted. The journal’s owner is believed to be the princess’s personal student, Twilight Sparkle. None of the town’s inhabitants have been located in the weeks since.

Readings:
Nimbus Productions
Scribbler Productions

I highly recommend both of them.

A print version of all the stories in this series can be found here.

Twilight reads about a way to view a pony's soul, to see everything about them laid bare. When she tries it on her friends, will she be able to look at them the same way again? Or will the secrets hidden in their hearts drive her away?

(Yes, I borrowed the idea of a "soulgaze" from The Dresden Files, because it's something that really fascinates me. It's not a crossover, just an idea.)

Now has a sequel!

Celestia has fought many powerful foes. Nightmare Moon. Discord. Chrysalis. But she has only ever feared one. When the nightmare from her foalhood returns for the lives of her pupil and her pupil's friends, what will Celestia do? Will she rescue the Mane 6 from a premature demise? Can she?

Credit for the brilliant cover art goes to my friend Martha at dingus-flavin.tumblr.com.

To save her sister and her faithful student, Celestia herself must travel into the ancient tunnels beneath the ruined castle in the Everfree Forest. She, and the guards who accompany her, must face the dark, twisting corridors. Still, what was Luna and Twilight's purpose at the old castle? Why were they unable to return of their own accord?

And what watches Celestia from beyond the light's edge?

"Equestria's Guard: the Bravest and the Best. Do you have what it takes?"

So the advertisements say. When Rainbow Dash saves the life of Princess Luna, however, she quickly comes to learn that there's a lot more to the guard than what everypony knows. As she faces down threats to her friends, her Princesses, and her country, Rainbow will have to decide exactly who she is loyal to.

A Price of Loyalty story.