In the 31st Century, humankind has spread to thousands of planets in the Inner Sphere. Once united under the glorious banner of the Star League, the Successor States and their noble houses now fight bitter wars over the scraps of empire. When a JumpShip carrying a special task force from the Federated Suns suffers a catastrophic misjump, the occupants find themselves stranded above a strange, beautiful world at once alien and eerily familiar.

Meanwhile, in the peaceful realm of Equestria, Ponyville’s resident bookworm , Twilight Sparkle, has stumbled upon hints of a secret buried for centuries. A secret that may lay bare long-forgotten aspects of Pony history and culture.

Our story begins on the planet Valexa, where the beleaguered Militia has launched a last-ditch effort to call for help against overwhelming odds.

Written with those who are not familiar with the BattleTech/MechWarrior universe in mind.

"... at the forefront of our fandom’s writing scene ... Masterpiece." —PCaRG
"... really enjoyable ..." —City of Doors
"...worthy of high praise." —PaulAsaran
"Lots of wonderful world-building, great action, well-developed characters and an engaging story." —Hoopy McGee

Steel Song is a lot of things. Earth pony. Uncle. Professional bodyguard.

Retired.

So when he receives a mysterious package from Princess Luna a few weeks after the changeling invasion, he's understandably apprehensive. More-so when he presents himself before the Royal Diarchs to find that not only do they desire him to come out of retirement, but to take command of a most unusual position...

A position that may have more significance than any of them suspect. Because strange thefts are occurring on the Equestrian Railway, thefts that nopony can explain. Thefts that may have far more sinister intentions than their seemingly innocent nature may convey.

Intentions sinister enough to shift the balance of power in Equestria forever.

Book I of The Dusk Guard Saga.
Epic Fantasy
Has a collection of Side Stories as well, the first of which is here.
Now with a TV Tropes page!
"This is 100% Approved by Twilight's Library!"
Added to Twilight's Library 11/26/2013
Added to Canterlot's Finest 12/01/2013

Chrysalis is beaten. Her invasion of Canterlot has failed. Her hive has been scattered to the winds. And with Equestria on guard, love is in short supply. She has failed her people, and now the future looks bleak and grim.

But there’s a change in the air. Chrysalis can feel it in her bones and in her dreams. Something is calling to her, drawing her and the remnants of her hive north. To the place the changelings once called home.

Placed sixth in the August 2015 Write-Off Event: Distant Shores.

Twilight finds herself struggling without a clear path in front of her as a princess. In a bout of panic, she seeks out her mentor, Princess Celestia, in the hopes of gaining answers, only to find herself with some much more distressing questions.

With a decidedly unexpected guest making herself comfortable in Canterlot Castle, it quickly becomes evident that her mentor has been keeping some interesting company over the years. Twilight quickly begins to realize just how much things are going to change for her. She's practically immortal. Which, apparently, means she's going to be spending a lot of time with beings a lot less mature than they first seemed.

(First Story-Woot. Likely to be broken down into three parts.)

Isolated from her friends and taken prisoner in the middle of a war, Twilight must deal with the very real dangers of being percieved as an enemy as well as the nightmares of her arrival on 'Earth'. Can she overcome her own fears and the fears of her captors? Will the wayward unicorn's assistance be a boon or a curse to the 'humans?' Most importantly, will she ever find her way home?

"In short, it's a story of friendship and plasma rifles, with the emphasis on the friendship. The characters are well written, the XCOM setting is fleshed out very well, and the story is compelling. If you love XCOM, you'll love the story, but even if you've never heard of it, it's more than worth giving the first 3 chapters a read.

There's excellent action later on, but the real strength lies in the collision between the friendly and naive world of Twilight Sparkle and the desperate world of humans fighting a losing war for survival and willing to do anything to turn the tide."

--Arzoo

(XCOM/FiM crossover)
(Cover art commissioned by a friend and created by the magnificent FoxInShadow!)
(Original cover art by the amazing Carnelian can be viewed here!)
(Gore tag for blood and some violence)
(Many thanks to the studius OminousTen, Arzoo, xXFluttershyForeverXx and finally Setokaiva for giving my rambles a once-over)
(Now with it's own TV Tropes page! Get to tropin' folks!)

It could have been just another night. Instead, Vinyl Scratch leaves a show to find herself suddenly presented with a chance to make a difference in the life of a filly no one else will look twice at. Now if only she can convince Octavia she's not making a huge mistake...as usual.

Note: This story now has an indirect sequel set several years in the future in The Most Unlikely Places. Cover art by SonicDash777.

Young Nictis had one dream: to serve his hive by becoming an Infiltrator, the most vital and vaunted role a changeling could aspire to. To hide in plain sight among the other species, blending in, while gathering the vital emotional energies that fueled his people. Few were deemed worthy of the dangerous job. He was one of the few nymphs selected for training, in the hopes that one of them would develop the skills needed to be entrusted with such a treacherous task.

But when a training expedition ends in tragedy, Nictis finds himself thrust into the role not to serve his hive and people, but to preserve his own life. Separated from the hive, alone, he must put what little training he has to the test. He must blend in with the hive's greatest source of food, and its most dangerous enemy: the ponies of Equestria.

(This story takes place in the same continuity as Fragments, but stands on its own. Reading that story isn't necessary for this one.)

TV Tropes page

Book cover art by viwrastupr

The Princesses find an alien creature barely clinging to life at the scene of a terrifying crash. Can the Combined Power of the Elements of Harmony save it, or more importantly, should they save it? Will the arrival of this strange creature tear Equestria apart?

TV Tropes
https://tvtropes.org/pmwiki/pmwiki.php/FanFic/Article2

Jessica finds herself flung into a world she has little concept of. Everything is strange and new to her, but worst of all she cannot communicate with the native inhabitants. A world of monsters and sapient ponies, griffons and other assorted beasts is no place for a human girl.

How will Jessica cope? Without an understanding of their language how will she make her way in the world, will she even be able to ever communicate with them? Why was she even brought into the world and is there even a way for her to get home?

(Thanks to Tulip for the Cover image!)

(Also now apparently has a Tv Tropes page in the making. )

Now has a re-telling in progress focusing on the Equestrians' side of things, A Stranger Among the Voices

Driven by an intense Warp storm, a Rogue Trader vessel finds itself crippled and stranded above a world no human has ever visited. The natives are friendly; can the visitors say the same? A Warhammer 40k/Friendship is Magic crossover. Yes, really
(12/02 added epilogue to last chapter)