Twilight Sparkle, Princess of Friendship, blinked her eyes a bit and rubbed her head against the cold window of the train. Only to yelp in surprise from the cold and quickly open her eyes. She looked around and noted the other passengers of the train were still asleep as she rubbed her now cold cheek with her pink scarf. Her wings staying tight to her sides to keep her body warm.
She sighed and looked out they window as her eyes met the falling cold snow outside the train. Despite how cold it all was she couldn't help but get a soft smile on her face as she saw the white stuff, she was a sucker for snow. Especially if she could play in it without worry. It was just so soft and fluffy, yet also oh so cold.
Though a small thought nipped at her mind as she looked to her saddlebags next to her. She used her magic to open it and levitate out a note from Princess Cadance, the note that led her to come alone to the cold and harsh tundra of the Crystal Empire and to it's only city...the Crystal City.
Dear Twilight,
It's been some time since I've seen you in the Crystal City after you defeated Tirek without our friends and saved Equestria once more. You've proven again and again that you aren't some ordinary Unicorn and that you're special!
But that's not the main reason for this letter. Remember the 'portals' you wrote to me about? The reason these humans have appeared everywhere? Well a traveler spoke of something in a cave near the Crystal City similar to those portals you spoke of and I believe you've been searching for a way to learn more about them yes?
Below you'll find directions from the City to the cave, it's not far. At best it'll be a few minutes through the tundra so bring your friends or at least Spike along with some supplies! You know how cold it gets at night around here so when it starts to get dark get back to the city and come to the Castle okay Twilight? You know Shining will worry about you if you're out in the tundra too long.
Your sister-in-law and ex-foalsitter Cadance.
Twilight couldn't help but gain a smile on her maw from the letter. Cadance did really care about her, but she had to go alone. That's why none of her friends nor Spike were aboard the train with her. This was just an experiment on a portal, she doubted that anything will happen. After all it's a harmless science experiment and she was a Princess so it's not like she can screw this up after doing so many times before in the past!
...Right?
The sound of the train's brakes and it's whistle snapped her out of her thoughts. She stuffed the letter back in her bags, closed them, and got up. The other train car occupants were waking up and grabbing their things, but Twilight managed to get ahead of them as she was already awake and escaped the cold train car, only to run into the cold weather of the Empire.
She shivered and wrapped her scarf more around her neck, heading away from the station and to the city limits of the Crystal City with the late morning sun above her. As she walked there she could remember how she, her friends, and her brother Shining were running from the Dark King and ex-Tyrant Sombra. Remembering how he tried to take the lone city of the Empire with dark crystals and dark magic.
She stopped at the crystals that formed an arch as an entrance along the road and furrowed her brows. The arch alone brought back many memories and despite how important Sombra was to the Crystal Empire's history there is so little actually known about him and dark magic!
For example, how did he get dark crystals? Did he make them? Did it have to do with dark magic? Did he make dark magic or is it a lost form of magic? Despite Celestia's disapproval of dark magic Twilight was so curious about it! Not to mention Starswirl the Bearded hadn't even written much about dark magic!
She had so many questions about it...but she wasn't here for that today. She shook her head and sighed mentally, "Get ahold of yourself Sparkle!" She cleared up her thoughts and looked to her saddle bags again, levitating out the note from Cadance to look at the directions.
"Okay so according to this note I have to head southeast from the city until I see a large cave with green light coming out of it? Sounds simple enough!" Twilight spoke aloud and cheerfully, this would be so simple! All she had to do was walk in one direction and she would find it.
She immediately sets off, keeping the note out for reference in case she forgot what she was looking for. But that would never happen to her. Thankfully there wasn't much snow raining down today so she had a long range of visibility, which would make her mission even easier!
Sometime passed as Twilight let out another deep breath, seeing the frozen air dissipate in front of her and become invisible once more. Before the young Princess does it again to entertain her boredom further she saw a cave with an ominous green glow coming out of it. This must be the cave that Cadence told her about!
She smiled to herself and started to trot to the cave faster, ready to begin her experiment. Course she knew what she would be doing would be frown on by her teacher but it was the only way to get it to work. Plus it was for science after all.
As she enters the cave she couldn't help but gasp. The Veil portal was in a better condition than she had hoped for! The green-like portal floated in the middle of the cave idly, as if waiting for something to happen. Gentle lines reached out from the portal to random areas of the cave like a newborn foal to it's mother.
Twilight slowed her trot to a walk as she levitated out a book she had taken from the Canterlot archives a few weeks ago. The front of the book was titled 'Basic Dark Magic: Tested by Princesses Celestia and Luna'
She opens the page to her bookmark in it. Reading over how to use dark magic again, the writing was obviously Princess Celestia's.
Entry One: Dark magic is clearly a dangerous kind of magic that should never be used. But it's clear that Sombra has done something with it and the Crystal Palace so Luna and I are attempting to figure it out in the event he returns.
All we know as of right now is that dark magic can be seen like a corrupted form of magic, yet any Unicorn or Alicorn could cast it at will. All it takes is a big enough burst of anger and/or annoyance (something Luna is very good at with me I might add!) or strong focus for a non-corrupted being to cast dark magic instead of their usual magic. Corrupted beings probably don't have to do this as Sombra casted it like it was normal magic when fighting us.
Perhaps he knows, or knew, something we don't? I'll have to find out some other time as I must lower the Sun now.
Twilight let out a loud, "Hmmm," and looked to the portal. So all it really took was just that? A burst of anger or annoyance and you could use dark magic, or just focus hard enough? The first part seemed off but she could just focus hard enough like she did last time.
She didn't know why. But these portals seemed to react to only dark magic. She had guessed this because her other tests with portals with normal magic of any kind failed to gain a response from the portals. Worse, it was rare for her to find one in a good enough condition to interact with.
But this one...this one was perfect to test it out on!
Twilight sets the book down and took a deep breath, lowering her head pointing her horn at the portal. She tried to focus hard enough on the portal, closing her eyes and seeing it in her head. Trying to imagine a burst of dark magic going from her horn to the portal itself.
She gulped audibly as she felt the tingling feeling of the unknown magic once more, starting to shoot dark magic at the portal. She dared to open her eyes and widened them in a mix of fear and surprise as she saw the portal.
The portal was reacting both positively and violently from the magic, growing wider and most certainly becoming active! Much more active then she planned. She stopped casting the magic and threw her head back up as she started to back away from the portal.
However it seems the portal won't allow her to do that. In a flash to blinding light, Twilight yelped and moved a hoof and her left wing to shield her eyes as she turns away from the portal. But what comes next is what she never expected to happen.
The Veil portal started to pull her in! It was pulling her, the saddlebags, and the book into it! She gritted her teeth and unfurled her wings widely in a desperate attempt to resist the pull of the portal, desperately trying to avoid being sent away from Equestria.
But it was no use. The portal flashed again, a sound similar to lightning following it. The portal pulled much stronger this time, causing Twilight to feel the ground leave her as she flew off of her hooves and into the portal! All she can do is keep her eyes closed as she felt herself being moved to...to wherever Equestria isn't...
She chuckled dryly as she pretty much floated, daring to open her eyes to see where she was now. However, all she could see what green, green everywhere. Beyond her position in this...empty place, she could see other Veil portals far from her location. Who knew where they led...
She sighed and spoke somberly, "Who would've thought I would be defeated by my own portal experiment? The prized pupil of Celestia and Princess of Friendship brought down by her own simple magic and portal tests!"
She grumbled and levitated the book and saddlebags over to her and looked into the book again, might as well read if she's stuck here. Without knowledge on how to get out she was stuck so she should at least brush up on her dark magic so she can open another when she finds it. Maybe it would help her get back to Equestria?
Entry Four: I worry about Luna. She wished to continue progressing in our research in dark magic despite the other dead ends and the danger. She's too eager to learn about it...I fear she wishes to try and find a way to reverse the effects of dark magic on Sombra.
I'm reluctantly helping her in it while trying to keep it slow, despite her grumbling. I just pray to the sun and moon themselves nothing bad will happen. She grew too attached to him all those years ago...which is partially my fault. I only hope I don't lose my sister to darkness.
She blinked a few times and read over the first paragraph again. "Reserve the effects on Sombra? What does she mean?" But before Twilight could try and answer it for herself or reread the second paragraph she heard a loud boom and looked her left, but then she wished she hadn't. What she saw before her was another portal opening, ready to spit her out into whatever world it connected this...'portal realm' to.
Closing her eyes, she braced herself for whatever pain might come from the rough landing that her interviews with humans said they suffered upon entering Equestria. Apparently the Veil portals aren't very good with landings. Course she wasn't going to be in Equestria, maybe she was going to the human world?
Her thoughts were interrupted as stinging cold air hit her coat, followed by a cold, hard, surface that caused her to yelp and reflexively tighten her wings against her body more. It felt...almost...like a cave? A cold, empty, tundra cave?!
She shook her head and opened her eyes, gasping in more surprise. She was back where she started! In front of her was her now ripped saddlebags and the book with her bookmark in it, though the bookmark was damaged and damped now...
She giggled to herself, she was about to be gone from Equestria forever and she's worried about a bookmark? She stands up and stretches, groaning lightly as her hooves argued against her in some pain.
Something wasn't right though, why did the portal bring her back here? She looked to where the portal is...or was?!
Her eyes widen again as she blinked a few times to make sure she wasn't having a concussion or something. But it was gone! The portal that spat her out here was gone! Her grumbled loudly and levitated the book up, putting it back in her damaged saddle bags. At least she was alive and in Equestria.
'But my research.....ugh!' she stomped her right hoof in frustration, 'A big opportunity lost for Celestia knows how long! Who knows when I'll find another one as good as that one!' she sighed and tried to calm down.
She looked to the outside world and slightly smiled to herself, speaking aloud, "Well...it wasn't a total loss. I did get to see the realm between portals and experience how it felt to go into one that is activated!" Her smile grew a bit more as she knew she did get something out of all this mess.
She decided to start walking, it was a bit of the way back to the city and judging by the light it was the afternoon. It seemed the portal kept her busy for some time, hopefully her brother wasn't freaking out. She giggled at the thought of him frantically searching the tundra for her when she was on her way back.
Sighing and seeing the frozen air particles evaporate in front of her, Twilight shivered from her cold hooves. 'I should've worn boots,' she grumbled to herself before looking up in hopes of seeing the city made of crystal.
What she saw however, was anything but lovely and free.
Before her was the Crystal City, but not the one she knew. Instead it's arch on the entry path and castle were covered in dark crystals. Not only that but guards patrolled the streets clad in strange armor she's never seen before with spears at the ready.
She looked over to the somewhat nearby train station, only to see no activity there. In fact the station seemed unkept and old, in need of repairs. But she knew what dark crystals meant, only one pony ever had dark crystals. But they banished him didn't they?
It didn't matter now though, because it appeared that the Dark King has somehow returned once more...and this time Twilight was the only one there that could stop him unless she could find her sister-in-law and brother...
'If they're not dead...' she thought, afraid of what might've happened while she was gone for most of the day. She stood tall and took a deep breath. She couldn't leave with the train gone, going south in the cold would surely get her killed eventually.
There was only one choice she saw, infiltrate the castle and try to find her brother and Cadance. She crouched and started to sneak towards the city, aiming to sneak through between the buildings. If she got caught then Celestia knows what would happen to her without Spike and her friends here to help her.
'Don't worry you two, she thought to herself quietly, 'I'll rescue you from Sombra...' She tried to reassure herself this would be easy as she tightened her scarf around her neck. But her mind knew that if he returned again this meant the crystal heart somehow didn't keep him away.
It fed fear into her heart because her mind kept asking herself one question.
How did he take the entire city and gain an army in a few hours?
Author's Note
Finally finished this first chapter. It's my first attempt in a long time to writing at third person. On the bright side I'm working on fixing my issue with the 's' and 'ed' at the end of words, kept changing them constantly as you can see in my past story and one-shots.
I don't plan to go back to my one-shots to fix them as it would alter the wording a bit and it's better to learn and show I've improved right? 
Either way, hope you enjoy the story (or short story) as I attempt to write down a history on dark magic and crystals along with our shadowy friend in an alternate world that is both different and similar.
On a related note I plan to do this story and then A Siren's Song, the sequel to Shimmering Sunset. But I'll admit I already thought of sequel for this story should it be successful.
