This story is a sequel to Stardust

When Equestria’s newest member of royalty asks for aid to be offered to her friends from abroad, the best and the brightest volunteer to serve. Captain Steel Song of the Dusk Guard are immediately mobilized to help XCOM defend their world from the enemies that besiege them. However, their first joint operation with the humans takes a turn for the worse and they quickly find themselves fighting for their lives against the full force of the monsters that threaten Earth.

(Stardust/Dusk Guard crossover)
(Coverart provided by a friend of Viking ZX!)
(While familiarity with both stories isn’t required, it is recommended)
(Many thanks to Arzoo for pre-reading!)
(All screenshots can be found at XCOM.wikia.com)
(Featured on 3/13/2013. Thanks everyone!)
(Now has it's own section on TVTropes as part of the Stardust series!)

This story is a sequel to Stardust

Times are changing for Equestria as Twilight’s return brings with it news of people and cultures from beyond the peaceful world everypony knows. Aid and volunteers are freely offered to help the besieged humans of Earth because every Equestrian knows that’s what good friends do. Unfortunately, making friends can also have the unintended consequence of making enemies.

When the monsters besieging the humans strike at Equestria with a level of brutality not seen in over a thousand years, the cry for help is sent to all the kingdoms of the world. Honored allies step forth to fulfill ancient treaties and oaths. Enemies, old and new, bury their grievances. An alliance never before seen in Equestria will be created to combat the monsters from the void.

And because of these events, a grim but welcome sibling to the XCOM project is born.

(XCOM/FiM Crossover)
(Sequel to Stardust, which I recommend reading before starting this. Fortitude Amicitia and Broken aren't required reading but are supplemental to the storyline)
(Gore tag for blood and violence)
(Alternate Universe tag because of the divergence from canon that Stardust has caused)
(Uses elements of Season 4)
(Coverart produced by the amazing Carnelian!)
(Many thanks to Arzoo, BradTheBrony, Vandenbz and Setokaiva for prereading!)
(As of 03/07/2016, the prereading team consists of Arzoo, BradTheBrony, Noble Cause and Metallusionsismagic!)
(Complete with it's own TVTropes page as part of the Stardust continuity. Could use some updating!)
(Character tags will be added as chapters are added!)
(Featured 5/12/2014! Thanks folks!)
(Possible spoilers in the comments! BEWARE!)

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!)

In the beginning, The Great Weaver brought together the world, from the mountains to the forests. Stitching it together, the Great Tapestry connects all living and nonliving things.

The Changelings found themselves especially connected to this Tapestry. Legend says that the first Changelings fell through the world as it was woven together, only to be caught on the First Weave beneath it all.

But what happens when something else is caught in the Weave?

Prince Phasmatodea, son of Queen Chrysalis, remembers what it was like before he hatched. He remembers being a human. He remembers dying. And he fully intends on avoiding another death.

But being gifted a new life does not matter when one failure, one false step, will lead to your untimely demise in the Changeling hive, for Prince Phasma must survive his toughest adversary from the start: Mother Dearest.

Cover art as of 1/18/21 by Nixworld

Rainbow Dash's morning was pretty much ruined.
She tripped getting out of bed and landed flat on her face, giving herself an aching muzzle.
She forgot to buy her favorite brand of hay flakes at the store yesterday and had to eat plain toast for breakfast.
She found out she had to pull double-duty today and tomorrow on the weather patrol.
Oh, and she found a nearly-dead foal, broken and bleeding at the edge of Ponyville.

The rest of her day became a whirlpool of stress and worry but the colt woke up, thank Celestia.
Something's not right, though. Nopony can find his parents, he's not in the registers, and there's an unsettling look in his eye...

-
YouTube reading by Fire Hearth

Chinese Translation by forgivenlove

Russian Translation by Likantrop

TV Tropes page, if you're interested in that sort of thing.

This story is a sequel to Necromancy For Foals

Twilight Sparkle and Rainbow Dash find themselves drawn by the call of the cutie map to a jungle in the middle of nowhere. Drawn further by the knowledge of an ancient temple, they are confronted with icy cold and a sense of dread.

A Necromancer was sealed away in this temple a thousand years ago.

Now, he is waking up...

((Sequel to Necromancy for Foals. Artwork by The-Minuscule-Task on Tumblr.))

Idol Hooves holds a special place in Equestria. He's probably the only exiled changeling to serve in the Royal Guard, or at least, that's what he expects, as exiles don't really broadcast that fact. However, it's well known that Princess Celestia loves all of her little ponies, and her guards perhaps more so, and that makes it one of the best ways for a changeling to discreetly feed.

But how does a changeling even get there, let alone get exiled in the first place? For that matter, why would it ever go to Canterlot? Set a number of years before the series proper, before Luna’s redemption, Idol details how he was exiled, the ponies he’s met, and the series of misadventures that led him to joining the Royal Guard, and should continue a good ways into the series, as something of an alternate perspective.

Soon, he’ll have to deal with a boisterous new princess to serve and a royal wedding in the works bringing a third to power. Will his old instincts bring this new life crashing down around him? What precipitates Chrysalis’s ill-fated assault on Canterlot? Is it really so wrong for a changeling to enjoy good craftsmanship to an obsessive degree?

New cover art provided by the fantastic Carnifex

And a TVTropes page here.

And an Ask Blog of questionable canonity!
Out of Idol Curiosity

Fanart by Norad2! Major thanks! Short For a Royal Guard

Art by Egophiliac of Idol and his Daring Duckie Please don't tell him what that brush is meant for.

Rating updated to (T), it's a bit darker than (E)
Comedy Tag added as well
And changed the character tags a bit.