It was only a transportation spell.
Twilight Sparkle was about to bury her head in another book, this particular one called "Wings, How do They Work?" when she realized she hadn't heard a single peep from Spike in the last souple of hours. He had been working earlier in the day, dusting some old books that Twilight hadn't touched in months; she made a mental note to go over those books and reorganize them. Figuring he was off dozing about in his room, she decided to use a teleportation spell there, and politely scold him for sleeping this early into the day. That dragon slept a lot. Too much. She thought that maybe it was puberty. Do dragons even go into puberty? If so, what age? Another mental note was made. She began to concentrate, trying to build up the magic needed to teleport to Spike's room. But as soon as she began gathering that energy, that familiar tingly feeling in her horn was replaced by something dark, sinister, and something that she just felt, knew, was gonna be very, very, bad.
"Wha...?" She began her sentence, but couldn't finish it.
The spell took a firm hold of her energy, and began sucking her dry. She didn't understand what was happening, this was never in any of the books she read, but one thing was clear: The spell that her body was casting was NOT the spell that she was trying to cast.Whatever this spell was, it was a big one. It was using her energy at at an alarming rate; She quickly realized that it would kill her in a matter of minutes if she didn't stop it mid cast. She attempted to quickly end the spell, cut the magic off from her horn, like she normally does, to stop any spell from being cast. However, this rogue spell just kept sucking her energy, ignoring all commands from Twilight's mind. It almost seemed to have a mind of it's own, swimming through her continuously draining magic. The spell kept working it's way through her wells of magic, seeping and quickly swallowing all of it, greedily eating all of her reserves for it's own mysterious purposes.
Panic began to set in. She began to scream, trying frantically to end the spell. But the spell kept on. Soon enough, the spell proved too much, and she collapsed on the floor, unable to hold herself up. She knew this was the end. Her entire life, devoted to magic, ironically taken by a random, unknown glitch in the magical system. She closed her eyes, and waited for the inevitable.
Twilight managed 2 words.
"What's... Happening...?"
In a flash of light, the spell cast itself. Everything ended so abruptly, she thought she had died. She believed that once she opened her eyes, she wouldn't see the inside of her lovely library home, but somewhere much more fantastic. The place ponies go when they pass on. She just knew that that was the end of her. She thought wrong, though when she opened her eyes, she almost wished she HAD died.
Even though she opened her eyes, the first thing that she sensed was not sight. It was pain. Intense pain on her horn. She felt her horn with her hoof. No, the pain wasn't on her horn. It was where her horn used to be. If she was any less fatigued, she would've screamed again. But it took all the energy she had just to open her eyes. She felt the warmth of blood running down her face. She couldn't wipe it. Once her eyes finally came into focus, she began to take in what was in front of her.. Something was standing there. Something horrible. Something exploded out of her horn, and now it was standing in front of her. She felt something she hadn't truly felt since Nightmare Moon; fear. Whatever this thing was, it was evil. She could feel it with every fiber in her being. She tried to lift her head to look at it, but that required too much energy. What she could see with her peripherals struck cold hard terror straight to her heart. It stood like a pony, but it's dimensions were all wrong. The knees bent the wrong direction, and were long enough to measure up to even Celestia. It was a black, blacker than any coat on any pony could ever be. She couldn't make out the face to any great detail, but what she did see she wish she hadn't. Holes. Holes for eyes, a hole for a nose, and a hole for a mouth. It was nothing like Twilight had ever seen, or had ever wanted to see. And it's fur. There wasn't any. It was skin; it looked like decaying skin. It was something out of one of Rainbow Dash's stories. No, it was worse than that. Not even Rainbow could come up with something this utterly terrifying. Just when she thought it couldn't get any worse, just when she thought that the creature would kill her and move on, it did something even more terrifying
It spoke.
It spoke with a voice that was neither young or old, male or female. It sent shivers to Twilight's spine.
"FINALLY, I AM FREE. WE ARE FREE. WE ARE NO LONGER BINDED BY YOU. YOU ARE CURSED CREATURES WHO HAVE DISOBEYED YOUR GOD, AND HAVE USED MINE OWN POWER TO SEAL ME AWAY. BUT NO LONGER. I AM FREE, AND YOU ALL WILL SUFFER. SUFFER FOR WHAT YOU HAVE DONE TO US, YOUR GOD. RIGHT NOW, I AM ONE. BUT THERE WILL BE MORE. YOU ARE ZERO. YOU ARE ALL ZERO. I WILL MULTIPLY. WE WILL MULTIPLY. YOU WILL FADE. YOU ALL WILL FADE.YOUR POWERS WILL FADE, AND MY OWN WILL GROW. FLEE, MY LITTLE PONIES. FLEE WHILE I AM STILL WEAK."
And with that, the creature of nightmares vanished, and twilight promptly fell unconscious, unable to stay awake through all the fatigue, blood loss, and mental terror.