Applejack has problems with a recurring nightmare.

It was just a normal day for Twilight Sparkle, and that's when she found an old book, a relic of Starswirl the Bearded. That's when it happened, that's when she became a Master, how Starswirl the Beared became her Servant, and why she must now engaged in a to-the-death battle royale against six other Master and Servant pairs – all in the name of some holy artifact with an incomprehensible power that must not fall into the wrong hooves.
A My Little Pony and Fate/Stay Night crossover, written to be comprehensible to those without any experience with Fate/Stay Night.

Authors: Stalin the stallion, Crushric
All art by Stalin The Stallion
Huge thanks to The Conflicted Writer

From the smallest of mistakes can butterfly the greatest of disasters. Even reality itself is not safe, for even the very Laws of Creation themselves are being thrown to the wind. Now, two worlds connected by the fundamental Laws of Creation begin to collide, bringing two antitheses together in a maelstrom of biblical proportions. And when that happens, nothing will matter but a glitch in the system, the very same ghost in the machine that brought these two worlds together. Only six brave mares can possibly stem the tide of ruin and face the very Laws of Creation themselves.

Reality is a lie. That's the one truth I've learned over the eons as the Spirit of Knowledge. Each life is held by a cosmic thread, and I just so happen to have the scissors. Reality is a lie: it can be bent with but the slightest of efforts. And with one modicum of effort, I can take a unicorn from her five best friends. With one final effort, I can bring her to her own personal hell – a world without her. And unlike Discord, I do this for “knowledge”. But where are my manners? My name is Metus. And you, Twilight Sparkle, are about to know what hell is: where your friends are not who they appear, where sun is forever set, and where there is no such thing as “good” and “evil”. Welcome to the other side of the mirror.

Obsession. That's a funny little word. It can mean oh so many things to oh so many ponies. They tell me that I've got an obsession. And you know what? They're right. With what, you ask? Why, that's simple: the Elements of Harmony. I have watched and stalked after them my whole life, only now do they take form.
My Whole life has been one long quest, one long lust, after the Elements. But is it not the powers of Harmony nor the mares themselves that I crave, no. I desire their antithesis: Gloom, Penury, Faithlessness, Facility, and Spite. I shall assign them to the ponies who best represent these forces. Why do this? Simple really. Because I must and because I can. Yet of these two forces the second in the greater; I do this because I choose to.
And in the end history will remember me as a hero.

Cauterium