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!)

In 2185, during his campaign against the Collectors, Commander Shepard discovered a previously unknown species whose origins predated any other race in the modern galaxy. Following a daring rescue from their ancient sanctuary, the Equestrian Herd was brought back into the galaxy where, for the first time in eons, they must walk their own path.

Knowing full well the terrible threat that lingers on the edge of the galaxy, the leader of this newly freed race fights to secure her people’s future while attempting to prepare for the storm on the horizon.

This is her story.
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The long awaited Sequel to Mass Effect 2: The Equestrian Equation This is a reader directed story. Your choices will shape events.
If you favorite, also like! It's one little button click that makes all the difference.

Also, this series has its own TVTropes page now! (Special thanks to user CrowMagnon for setting it up).

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!)

Brought to you by Loyal2Luna, this new Downloadable Content for Mass Effect 2 brings the fight to Equestria.

Just about ready to embark on their mission to stop the Collectors from further abducting human colonies, Commander Shepard and the crew of the Normandy SR-2 are given a new priority, when the Illusive Man tasks them with investigating the mysterious disappearance of a Cerberus science team.

Soon, what begins as a simple search-and-rescue unveils a mystery millions of years in the making, and the Commander finds himself thrust into a situation he couldn't possibly have prepared himself for.

Join the Hero of the Citadel as he uncovers the secrets, combats the demons, and ultimately decides the fate of the impossible world known as "Equestria."