Alric, the Chosen Undead, had spent eons in the broken time of his world studying the Curse and searching for a cure. In his research, he learned the horrifying truth. Gwyn had cast the curse upon mankind when he linked the flame to perpetuate the Age of Fire, fearing the natural cycle and the rise of the Dark. In doing so, he damned the world to a slow and agonizing apocalypse, merely for his own lust for power and inability to allow the cycle to happen as it should.

Thus Alric made it his purpose to undo the curse and restore the natural cycle of light and dark to undo the damage Gwyn had wrought. But in the final moment, while he was on the verge of accomplishing his goal, he stumbled into a trap laid upon the First Fire by Gwyn to prevent what the Lord of Cinder had set into motion from ever being undone.

Alric was cast through time and space to a universe not his own. Landing in the Frozen North over one thousand years before the rise of Twilight Sparkle and her friends.

Can he find his way back to fulfill his purpose before it's too late? Or will he succumb to hopelessness and go hollow upon realizing there is no way back?

And what of the two adorable fillies he found within the frozen ruins of a village destroyed by windigos, and saved from freezing to death? What shall become of them?

Tanya Degurechaff gets tossed into Equestria and transformed into a Changeling Queen. It's a nice retirement from modern warfare as an aerial mage. Then Queen Chrysalis attacks and forces her out of retirement. Historians refer to this as 'a bit of an oopsie.'

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!

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

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.

Source Code, the pony from another planet... Planet Earth. He was once a game developer for a small indie game company that he and his friends made together. Now, a blue coated unicorn with a yellow mane, somehow finds his way into being tutored by Princess Celestia herself. He soon finds out about magic, and subsequently learns about how performing spells is grouped into three different groups. Rune Based Magic, as he soon discovers, is very close to his old hobby...

Coding.

Will Source Code make a name for himself? Will he live life out like he had on Earth in a dead end job? How is he coping about being forcefully ripped from his comfortable, though boring, life on Earth?

Disclaimer: 'coding' is being used very loosely.

Life is full of surprises. That is a known fact. However, you always expect some kind of minor surprise, like your train arriving a little too late, or your ice-cream having vanilla taste rather than strawberry. But sometimes, life will give you surprises you could never predict. For Fluttershy, it was three little foals. But not her own foals, or even orphans. Three little foals that used to be her and her friends' most fearsome and dreaded foes.

Sombra, Chrysalis and Nightmare Moon.

Will Fluttershy's nerves survive this onslaught of misadventures? Will she keep the three villains hidden? Will she even become friends with them? Why do I sound like a narrator to a bad criminal drama? Don't think or try to answer those questions, just go ahead and read!

Edited by: MessoriaAQ, Cerulean Voice, Gidget_TheGear, Twilight Fashion

Cover art by amazing Missangest!

Cover art got featured on Drawfriend in EqD!
The story itself got proudly rejected by EqD!

Sunset Shimmer has finally rebuilt her life at Canterlot High. She has friends, she's in a band, people like her, everything's going great...

And then out of nowhere, she turns back into a small talking unicorn.

Now, with the help of her friends, she has to figure out why she's suddenly a pony in a human world, and whether or not she can become human again...or will have to leave her new life and go back to Equestria.

(Cover art vector sources: Elsia-pony, TheShadowStone)

Now with a TVTropes page!

Principal Celestia has accidentally fallen through the mirror into Equestria, and it may be a bit before she can go home. Until then, she has to learn to cope with a strange world, in a strange body.

At the same time, Twilight has to figure out how she can help her new guest while keeping Equestria from freaking out over the presence of a second Celestia, and Sunset Shimmer has to figure out how she is going to make amends with those she had left behind in Equestria, while keeping an eye on her Principal.

Disclaimer: Since I wrote this description ages ago before I even knew the plot, the story is mostly pure comedy in the beginning, with eventual Sunlight and Chryslestia shipping!

Cover image by Arvaus, used with permission.

With nothing happening, no world-conquering villains or Crystal Hearts being shattered and so on, Twilight is bored. She has nothing to do, plainly. But while in the middle of a drab reading session, she notices something doesn't feel right. Not to her, but in the night sky. She can't see it, but she can sense it. Something not from this world has entered her world, and it could be the first ever message from aliens.

And perhaps those aliens are trying to say hello.

(Btw, look up "Pioneer Probe Plaque" if you want the image described here. I can't post the actual thing because of mild nudity in it, but you can search it for context.)

(Review by PaulAsaran!)