When Twilight visits Celestia's private hall of stained-glass windows, each bearing the image of a long-gone friend, one in particular catches her eye.

Who was this pony?

Why was she so important to Celestia?

And why does she look so familiar?

There is now a Spanish translation of this story, courtesy of Spaniard Kiwi

Twilight, Spike, and their friends leave the School of Friendship to embark on another adventure. To fill in during their absence, Twilight assigned a substitute teacher to cover for her and teach her History of Friendship class. When the students find out they begin discussing what pranks they should pull or how they can convince what they assume will be a pushover substitute to go easy on the homework.

The pony who walks through the door is not who they were anticipating.

When Twilight Sparkle was just a kid, her best friend was a girl named Sunset Shimmer. Though their friendship had a bit of a rocky start, they quickly became inseparable, no matter how much everyone thought of them as ‘weird’. They were there for each other.

Were.

Years after the tragic accident that tore them apart, Twilight is determined to move on from her loss, and she sets off on an independent research project to investigate the strange happenings at Canterlot High. Little does she know that she will soon come face to face with what appears to be a literal ghost from her past.

Coverart by Kare-Valgon. Chapter illustrations by Zorbitas.

Edited and Pre-read by Dubs Rewatcher, r5h, and Kalan.

Takes place after Rainbow Rocks, but was written before Friendship Games and does not take it into account.

Chinese translation

Print copies now available.

When Princess Celestia comes down with a mysterious illness despite her immortality, her loved ones flock to her side, including Sunset Shimmer. With only so much time left, Sunset takes it upon herself and Twilight to get to the bottom of it. The two of them work together non-stop to find a cure, which would be fine, if Sunset had gotten around to telling any of them she's dating the other world's Twilight.

Edited by the kind and insightful Space Jazz. Cover art designed by the incredibly talented Kiki-Kit and modified by the masterful Amber Spark! Spoilers in the comments.

Hi, my name's Nightingale and I think my Mommy's the best Mommy in the world. She doesn't just have one face, but many. And she always saves the very best face just for me.

Mommy has a great big list of ponies that hurt her before she adopted me. I really hope she gets to meet them all again. To make them apologize.

Artwork by LaurenMagpie.

Daring Do cannot believe her luck when she is asked to help explore the most ancient tomb known to ponykind. But terrible danger awaits her, for beneath the earth rests something beyond equine understanding.

Warning: comments contain ending spoilers.

TVTropes page.
Alternate ending by Duplex Fields.
Archived in the Pony Fiction Vault.
Reviews:
One Man's Pony Ramblings
Louder Yay
PresentPerfect
The Royal Guard
Cleverpun's Critique Corner
The Goodfic Bin

After a long day of flight practice with Scootaloo, Rainbow Dash discovers the filly knows next to nothing about preening and takes it upon herself to teach her.

Warning: May Contain Feels and/or D'aww moments.

Featured on FIMFiction on 7/20/2013. Yay!
Featured on EQDaily on 09/12/2013 Double Yay!
Reading by TheLostNarrator (excellent!): Here
Reading by DRWolf: Here
Reading by Joehighlord: Here
Riffed by Draklox: Here
Korean Translation: Here
Spanish Translation: Here
French Translation: Here
Chinese Translation: Here

"Dear Santa Hooves. My name is Apple Bloom, and I don't want presents for Hearth's Warming this year. I just want my cutie mark..."

Featured on Equestria Daily -- January 18th 2013
Fanfic reading by Scribbler
Reddit page
Download link for the 'FROM THE DESK OF TWILIGHT SPARKLE' paper

Every night, in a little stable just outside of town, an old mare lays down to sleep. And every night she has the same dream of rainbows and open sky...

Obiter dicta -- things said in passing.

A collection of short stories, vignettes, and delete scenes, mostly based in the Civil Serviceverse and tending to be either slice of life or comedy. Also contains contest entries including FanOfMostEverything's Imposing Sovereigns.

Currently contains:

1. An Afternoon For Dotted Line [slice of life] [comedy]
2. The Game The Princesses Play [comedy]
3. On the Inaccuracy of Proverbs [slice of life] [comedy][sad]
4. The Nature of War [history]
5. On Forensic Accounting & Choral Singing [comedy]
6. Hoofprints [human][sad]
7. Dr. Spinning Top—Specimen Annotated Daily Schedule [slice of life]
8. Love and Other Acquired Tastes [comedy][sad]
9. Any Other Business? [comedy]
10. Songs Like Snow [romance]
11. Civics [comedy]
12. The Other Princess [slice of life] [comedy]