Ten years after Twilight Sparkle became a princess Equestria is at the edge of a war. Many innocent ponies are killed in the most horrifying ways and the Elements and Princesses can't seem to find out who did it to the ponies. But when one of Equestrias most loyal and trusted turns against them and joins the dark side almost everyone loses hope.

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Grendeer
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My exemplary artist:
DearMary
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The Bearers of the Elements of Harmony failed to stop Sombra in time from getting into the Crystal Empire and acquiring the Crystal Heart. Now the Crystal Empire is ruled over by a tyrannical unicorn, that will stop at nothing to get what he wants.

Equestria is on the brink of war, and the only ones who can stop the evil king of the Crystal Empire, are six mares. Those six mares are the Element Bearers, but can they use the elements while one of their own is missing and in fact within their enemy's grasp?
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This story is a pickup from Pat_Hoof_5000, with his generous permission of course. I aim to finish what he started.

Collab with the awesome pony known as LightningBass94

That Romance tag isn't there for the reason you probably think it is.
Also, this story was added into groups that it no longer fits into. It was added to these groups by the previous author.

Upon her first use of darkness its taste lingered within her mind, creating an ever growing thirst and revealing her true desires. With her recent elevation to an alicorn and princess she begins to find her desire for power insatiable. Small seemingly inconsequential steps grow into giant leaps, pushing her senses of morality and reason.

Besides, doesn't the ends justify the means? For a queen can accomplish so much more than a princess....

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Special thanks to Omny87 on DA for the inspiration.
FEATURED: 7/1/2014 THANK YOU ALL!

King Sombra, after witnessing the fall of Twilight Sparkle, manipulated her emotions to make her his apprentice. Over the years, Twilight's knowledge of dark magic excelled at an astounding rate. But with such power has a toll on the body. Her hair and tone colors lost their hue, her eyes began to glow of dark magic, her horn glowed red when using magic. The power of shadows was so great within her, she could match her power with the Elements of Harmony. No longer was she Twilight Sparkle. Instead, she was the Herald of Shadows...

Twilight, my Faithful Student, my friend, if there is anypony that can create a world of Harmony, true Harmony, it is you.

More than a thousand years ago, my sister and I sought to create a perfect world, a world ruled by Harmony. A world free of evil. We were powerful and believed ourselves above the laws that governed this world. But this world is governed by the laws of Magic, and Magic, it seems, demands balance.

Where there is Light, there is Darkness.
Where there is Order, there is Chaos.
For there to be Love, there must be Hate.
For every Dream, there is a Nightmare.
Each begets the other.

And like boiling water over a fire, each can extinguish the other.

I should not have been surprised when the day came that the evil I had to fight was my own sister. It was the world restoring the balance we so foalishly ignored.

Perhaps, it is for this balance that I now stay my hoof. I have chosen to have you,Twilight Sparkle, act in my stead as the evils I thought vanquished, inevitably return to Equestria. It is in hopes that you may learn this balance, that you may learn from my mistakes. It is not something I alone can teach you, when I myself still understand so little. It is why I must now rely on the help of an old nemesis.

He intends to take you away, my protégé, and make you his own. You must not succumb to his influence. Yet if you are to learn the balance that is at the essences of all things, it will be through him. For the future of Equestria and for the sake of Friendship, you must prevail.

I hope that some day you can forgive me.

What if Twilight was never meant to become an alicorn through friendship?
What if she wasn't meant to help reform Discord?
What if King Sombra was to return to power?

A dark destiny awaits you now, Twilight. You weren't prepared for this.

Sombra may have been defeated after his attempt to retake the Crystal Empire, but he was not destroyed. He still lives, and now he seeks to work his way into the mind of Princess Twilight Sparkle. As she struggles with the implications of her new immortality, she finds less comfort in the wise words of Princess Celestia, and is drawn to the dark magic of a fallen king.