The princesses gave their magic to Twilight to prevent Tirek from stealing it. As a result, they end up stuck in Tartarus.

Marvelous place, Tartarus. Really brings ponies together. The fact that things manage to go downhill here says a lot about the wonders of family and alicornhood.

Spanish translation by SPANIARD KIWI

Audio Drama by Espa_Roba_5 and Ajvasquezbrony28
Live reading by The Living Library
Live reading by Astro-Brony

Proofread by Octavia Harmony

This story is a sequel to The Traveling Tutor and the Diplomats Daughter

“You should have burned their aerie to the ground two centuries ago and killed every one of them when you had a chance, Tia.”

These words trigger a series of events that send four ponies to the far northern Misty Mountain Aerie where Wingmaster Talon is threatening to invade the newly discovered Crystal Empire. The Diplomat, Luna's Hoofmaiden, and two Royal Guards are to face hostile griffons and dangerous mountains in order to bring peace to the region and prevent a war.

But what they find in the mountains is far worse than they could imagine, and their only chance for survival becomes a race to escape in a battle to the death.

Featured on Equestria Daily [Adventure][Sad]

Written to stand alone, but follows :
The Traveling Tutor and the Diplomat’s Daughter
Diplomatic Security
Genealogy (or the mating habits of Nocturnes Pegasi)
To Sleep, Perchance to Dream

Editing assistance provided by Peter and Tek.

Original line drawing by Ralph Hayes Jr.
Background Summer Campfire by BonesWolbach
Colors and shading by Shaleclaw
Special mention to JoyfulJ for shading on Pumpernickel’s armor.

Twilight Sparkle was quite positive she could handle the job of teaching young unicorn students in Ponyville how to handle their new magic, but when the school’s traveling magic teacher returns to town as scheduled, a series of miscommunications and accidents nearly drive the two of them crazy. Only the power of friendship (and a certain amount of tinkering from the townsponies) can save the day for them and their students before complete disaster strikes, but maybe there is a little more than friendship in store for the two young teachers.
[Comedy][Education][Slice of Cake] Featured on Equestria Daily. With a TV Tropes page and two sequels, The Traveling Tutor and the Diplomat's Daughter and The Traveling Tutor and The Royal Exam.

A lighthearted look at education, young love, dating and buckets of water in the face in that most normal of all small towns, Ponyville.

Caution: Contains bananas, marble chips, jogging, matrimonial planning, romantic interference, intrigue, lesson plans and lots of nuts. A whole town full of them.

Rated I for Innuendo, some drinking, some sleeping together (Just sleeping! Really! Why won’t you believe me?) and a great deal of dunking in the town fountain.

No cupcakes were harmed in the production of this fic. However, a great number were eaten. And they were yummy.

Cover art by Tamalesyotole on DeviantArt
Available in paperback at Lulu.com at cost

This story is a sequel to The Luna Cypher

Twilight sets out to learn more of the ways of the world, and soon decides that the whole planet is disorganized, insanely dangerous, and desperately needs to be fixed. And she's just the mare to do it... with a little help from her friends.

Also, there are sky-pirates!

Book 3 of the Alicorn Adventure series.

A few extra, slice-o-life chapters are here: On the Rocks

This story is a sequel to The Celestia Code

When the monsters created by the dark crystal engine escape their prison, it's up to Princess Twilight Sparkle to deal with them. She gets help and advice from Princess Luna, but things don't go as planned. In fact, when a pony who relies on logic and rationality tries to navigate the stormy seas of emotional entanglement while simultaneously saving Equestria from a horde of evil creatures intent on destroying everything they encounter, nothing goes as planned.
AUDIOBOOK by VisualPony
WARNING: Major spoilers in the comments.

Book 2 of the Alicorn Adventure series.

Goodreads Page
100% Approved by Twilight's Library!

The Badass Twilight tag applies more than ever, but please note the new tags.

This story is a fairly direct continuation of The Celestia Code. You might be able to follow it without having read The Celestia Code first, but it's better if you do.

The sequel is here: The Twilight Enigma

Most excellent pre-reading/editing done by the erudite AcademicPony and the dapper statoose!

Princess Twilight Sparkle discovers a centuries-old mystery hidden in the Royal Archives. Her investigation leads through layer after layer of deception and misdirection, setting her hooves on a path that seems to be leading to a mysterious secret. Along the way, she learns that some friendships can be very, very strange.

Book 1 of the Alicorn Adventure series.

AUDIOBOOK by VisualPony
Featured at the Royal Canterlot Library
TV Tropes Page (Courtesy of Sandtalon)
Goodreads Page (Courtesy of Facedeer)
Equestria Daily Page

WARNING: Major spoilers in the comments. Takes place several months after the end of season four. (Not a Da Vinci Code crossover, BTW!)

Do you see a dark tag? No, you don't. Not dark. Well, okay, there are a couple of dark-ish bits, but that's all. Not enough to warrant a tag. Speaking of tags, there really ought to be "Badass Twilight" and "Friendshipping" ones.

Sequels and side-stories (and more) can be found here Offprint and AO3, and a hardbound two-volume set of all that can be ordered from The Ministry of Image.

My editor for the first edition of this story was Gogito, and I can't thank him enough for all the hard work he did. My editor for the revised version was PresentPerfect, and he did a terrific job of getting the story into excellent shape.

This story is a sequel to Past Sins

When pursuing Starlight, Twilight and Spike experienced variances of Equestria, and saw how the river of time could have been different. Now, Starlight has moved in with Twilight, Nyx, and Spike and has begun her studies in friendship. To thank those who have helped her embrace friendship once more, Starlight has created an enchantment that allows the castle’s map table to let anyone glimpse other variances of reality.

The power to ask “what if,” can be a source of great amusement… but for some, the hypotheticals are haunting reminders of what could have been.

On a dark night filled with even darker magics, an insane cult attempts to give Nightmare Moon a body and life of her own, utterly separate from Princess Luna. But, when the spell is interrupted by Celestia, something unexpected is created.

Now, a little black alicorn filly named Nyx finds herself living under the care of Twilight Sparkle, only to be haunted by memories and emotions from her past. Is she Nightmare Moon reborn or is she simply a doppelganger with a soul and mind of her own? Can Twilight Sparkle protect Nyx from those who refuse to see past her dragon eyes and black coat?

Or, will Nyx be forced to inherit the sins that may not even be hers and become the greatest evil Equestria has ever known?

This story is a sequel to The Monster in the Twilight

Now that Luna has returned to the throne, and the aftermath of her brief appearance as Nightmare Moon is being cleaned up, the story is over. Right?

Not quite.

Twilight Sparkle had nearly been destroyed in the chaos of Nightmare Moon’s return, but now with the assistance of her five friends, she is facing a fascinating new world filled with wonderful things. No longer the scarred monster who nearly destroyed Canterlot and raged through the Everfree Forest for over a decade, now she has been healed by the Elements of Harmony and is living at the edge of town with her adoptive mother Zecora. Not all the fears of her past can be left behind that easily though, and now she must face the consequences of her actions as she faces the most daunting challenge of her life.

Ponyville.

Letters is a sequel to the alternate universe story The Monster in the Twilight. In this story, Twilight Sparkle exchanges letters with Princess Luna, two ponies with a common problem of fitting in and making friends after the destruction of Nightmare Moon.

Normally I would try to talk you into reading the sequel even if you haven’t read the original story, but in this case, you’ll probably be more confused than entertained. But go ahead. I don’t mind if you don’t read the first story. You’ll never find out what an Urlock is, but that’s fine. It’s your funeral.

Editing Assistance by Alicorn Priest, Peter and Tek

Credit for the incredible picture All Night Study Group goes to Bibliodragon at Deviantart

Physical books are available on Lulu.com (up to Chapter 82)
Letters From a Little Princess Monster (Paperback) 726 pages
Letters From a Little Princess Monster (Massive Hardback) 780 pages

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)