September 4th, 2551. VDF Stronghold, Harmony.

Sunset opened her eyes and groaned. She groggily sat upright. She moved herself over, her one leg hanging off the bed. She looked at the steel buckle on her stump and sighed. She removed her footlocker from underneath her cot and clicked it open.

Inside, was her robotic leg, arm, and her mementos.

A photo of her getting medals for successfully destroying the UNSC fortress, for a few other things. A picture of her in the uniform she got when she was promoted to Sergeant, one of her sitting beside Flash Sentry, the medals, a modified M6D Magnum, and a bible, burnt to a crisp, with a single depression in the cover, where a bullet struck it.

Sunset grabbed her prosthetics, attached them, and stood up. She clenched and loosened her hand a few times, then pulled a few kicks to make sure nothing was wrong, and stretched. Her body still burned occasionally from the wounds she'd obtained, the two years ago, when Sunset destroyed that fort. She smirked to herself, and dressed herself in a bodysuit.

When she first awoke, they asked Sunset hundreds of questions. Were the base's files not intact, they probably would've just executed her for being crazy.

Sunset stretched her arm and attached her radio headset to her head, her cap over it. Sunset grabbed her leather jacket and slid that onto her shoulders, over her bodysuit.

Sunset grabbed her BR55HB from under the cot, clicked the safety off, and slung it over her shoulder. She pressed a few buttons on the keypad by the door, which soon after, parted and met with the walls. Sunset walked out into the corridor. She turned to the Armory, when her radio lit up.

"Sergeant Shimmer! Report to debrief at once." Sunset responded with silence, spun on her heel, and started her walk to the CIC. She reached a bunker door, flanked by two soldiers in heavy, bulky Argus-Class Body Armor, Mark VIIs, AIE-486H Heavy Machine Guns in their arms, attached to packs of ammunition upon their backs.

"I'm reporting to the CIC for debrief." she pulled out a small device that sat in the palm of her hand. It projected her information for the two troopers, who then stepped out of the way and opened the door.

"You may proceed." Sunset shoved the device into one of the pouches on the waist of her bodysuit, and walked through a set of doors marked "Combat Information Center".

She was met with several VDFMC Commanding Officers. The lieutenant, whom everyone nicknamed "Luna" stood at the end of the holotable. Then, there was the General. Sunset immediately saluted.

"Staff Sergeant Sunset Shimmer, reporting for duty, ma'am!" The General laughed.

"At ease, Shimmer." she, and the rest of the soldiers already in CIC were in full combat gear, with weapons on their backs, or hanging from their hips.

Sunset walked over and looked down at the table. She looked up at the general, who was at least seven or eight feet tall.

"What's the situation, ma'am?" Sunset asked, looking at the hologram on the table.

A CSO-Class super-carrier, currently being engaged by the VDF Di Vinci, The Machiavelli, and the Notre Dame, along with thousands of small vessels that Sunset knew not the name of.

"We're currently being attacked by not one, but two CSO-Class Super-carriers, and it appears they may be winning." General Celestia stated angrily, placing in a set of commands into the terminal at the end of the table.

The image changed to a star-shaped crystal, encased in a golden crown.

"We found this within one of our experimental Slipstream Space destinations, and—" Luna cut her off.

"—And we want you to get it, so that we may use it against our enemies." Celestia frowned at the lieutenant, who in turn smiled innocently.

"When we sent a few Rangers through, they immediately came back out, all whispering your name, as well as completely brain-dead." Celestia gave Sunset a weary look.

"Sunset Shimmer... They just chanted it, nothing less, nothing more." Sunset paled, unknowing of why.

"Sunset, we need you to go through that portal, and find us that crown. Do you understand the orders given to you?" Sunset hesitantly nodded.

"There isn't time to get you fully combat ready, so just take these and follow us." Celestia handed Sunset a few magazines of 9.5x40mm cartridges and started walking over to a panel in the wall.

Groooooaaaaannnnn.

The panel slid away to reveal a narrow corridor.

"With haste!" Celestia led Sunset down the hall. It brought back a sickening sense of Deja Vu to Sunset, and she felt memory flashes back to that wretched base—

'No, calm down. Don't think about that damned place...' Sunset shook her head of these thoughts, and Celestia squeezed past her, typed in a few numbers on a keypad, and a second door opened with a groan. It seemed to have been here only a short time, yet, also felt like it hasn't been touched in what seemed like years.

Sunset walked through into an open room.

The room was made of some sort of steel-composite, with paint covering the ceiling. Toward the end, tubes, wires and a lot of tech sat around, humming aloud. In front of that, four small angle-pieces were sustaining a large, ovular cyan portal, cackling with energy. The COs that went in took shelter in a command box at the back of the room.

"We're counting on you, sergeant. If you do not make it, may your soul forever rest in Valhalla..." The lieutenant started going off on a rant, or a lament, Sunset couldn't tell.

She carefully approached the portal. It showed her distorted reflection. Sunset closed her eyes and threw herself in.

Somewhere... CALENDAR INFORMATION FALSE. Calibrating... Calibration Failed.

Sunset felt weightless. Everything around her was black, and her body felt... wrong. She realized what was going on, and opened her eyes groggily, groaning in pain.

She felt much shorter, and... longer? How to put it... Sunset looked down at herself, and held back the urge to scream. Or faint. Or both.

She was a quadruped, with wings and a horn, a flowing, fire-like... mane? upon her head. A modified version of her uniform sat upon her body, along with a robotic stump on either of her legs. She got to her... hooves, and stumbled a bit. She looked around, and saw a marker through the HUD shades upon her face.

Sunset began stumbling through the halls, carefully avoiding the patrolling guard, which seemed a bit... incompetent, maybe? Sunset shook it off and continued to move toward the marker, until she came to a pair of double doors.

She fumbled with the handles for a moment, then finally opened the door. She quietly... trotted in, looking at her surroundings.

She was in a bedroom, full of books, with a purple horse sleeping in a bed, with the same features as her, except she seemed... shorter, almost. Not only that, but Sunset found a little purple... That's a dragon. In a dog bed.

Sunset found her hair acting as a source of lighting, so being able to see—not that it was difficult in the first place, with her augmented sight, and all—wasn't very difficult. The lance corporal trotted over to the nightstand and stared at her objective as it lit up with a yellow glow.

It seemed to levitate into one of her pouches, and relief filled her mind—until she tripped over the dog, and knocked over the dresser.

"H-Huh, what..." the little dragon woke up and watched as Sunset scrambled to get out. The horse did as well and yelled.

"Stop! Thief!" Sunset groaned and tried running. She failed, then smirked to herself and slid across the too-well polished floor. She laughed and glanced back. The horse wasn't there, until it was, right in front of Sunset—

CRASH!

Sunset went flying, sliding across the floor. She stood up, stumbled a bit, and turned to the portal. The horse got wrapped around a drape, and got stuck.

"Sorry if I can't stay to chat, but it appears you're a bit tied up at the moment." Sunset chuckled at her own pun, and saw a group of eight horses, two tall ones—Both a few inches shorter than Sunset— and six smaller, multicolored ones. Sunset stared at the white one for a moment, inciting a headache.

"Ta-ta!" Sunset let herself fall back through the portal...

And darkness overwhelmed her again.

Harmony, VDF Fort Galileo, 2551.

Sunset groaned. Her bones ached, and her muscles burned. She sat upright and held her head as a headache began plaguing her mind.

Luna and Celestia were gone, and Sunset heard gunfire outside. She shouldered her BR55HB. She felt glad to be back in her body. Her real body, that is. Sunset pulled the objective out of the pouch on her uniform. It had changed shape, apparently. It was now some sort of...

The room itself was ripped up, with panels of the ceiling now on the floor, along with pipes, tubes and all sorts of other gear strewn about. The portal was now closed behind Sunset, which she really hoped stayed that way.

Sunset clicked the safety off her BR and crouched down. She carefully made her way over to the door, stacking up. She poked her head and rifle out. Empty.

She rounded the corner and started moving down the narrow corridor with haste, flashlight on. She shoulder-rammed through the next door, and saw several Unggoy and a Sangheili minor around the holo-table.

Sunset wasted no time and fired three quick bursts, killing each Unggoy, then took cover as the Sangheili roared. It began firing it's Type-25 Directed Energy Rifle at Sunset in bursts.

Sunset waited a moment, the poked her head out and discharged her weapon.

The Minor's shields flared, and he raged. The warrior hurdled the table and picked Sunset up by the throat. The assassination blade on his wrist activated.

Crack! Crack!

The minor gurgled blood and crumpled to the floor, dropping Sunset. She looked over, and saw someone familiar.

"Major." Sunset addressed, getting to her feet. She picked her BR up and shouldered it.

Flash Sentry stood at about six-foot-three, a bit taller than Sunset. He currently wore a suit of Argus-Class Body Armor, with a Void-Dancer Variant helmet. His armor was a light gray, covered in scorch marks. Several of the thinner plates were smoking from plasma burns. In Flash's hands, was an M6C magnum. His shields seemed to be down, as his armor was cackling with golden electricity.

A subtle hum filled the air as his shields recharged. Sunset walked over to him and frowned.

"Is the armory still operational?" she asked.

"Yeah, just about one of the only things left operational... Covenant have been bombarding us with mortar fire for hours. Where the hell have you been?" Flash retaliated, irritation filling his voice.

"On a special assignment." Sunset walked past Flash, BR55HB raised and sweeping over each surface. Blood stained the walls and the ground, human and Covenant. Bodies lined the floors, along with spent shell casings, scorch and bullet marks in the walls and floor, along with discarded weapons. The facility would shake occasionally as a bombardment from Covenant assault.

Sunset drew her knife and thrust it forward, only for a three-fingered hand to grab her forearm and shove her down. She scrambled back and began firing her rifle at the Sangheili, a war cry filling her throat. The Sangheili fled to cover. Sunset quickly got to her feet and planted her shoulder against a wall opposite Flash.

"Where'd it go?!" she yelled, firing a few bursts that went wide. Flash knelt down and fired his MA5C at random, in the general direction of the Sangheili.

"I've got no idea!" Flash quickly turned the corner and rushed forward to a metal box that provided cover. The Sangheili popped his head out and fired at Flash from the end of the corridor. Sunset decided now was a good time to use that crystal. She held it within her hands, taking a few deep breaths.

Then, she got mad. These Covenant motherfuckers were trying to take her home from her, the one she lost —literally— an arm and a leg for! She was NEVER going to let that stand.

Sunset felt her head heat up, and she put the crystal in her back pocket and looked down at herself.

Her uniform had melted down into a bodysuit, and glowing, transparent flame-like armor was now attached to it. Sunset just shook it off as one of the less random things she'd seen today, and rushed forward at breakneck speeds. The Sangheili was stunned, and began backpedaling, firing his plasma rifle at Sunset. The rounds seemingly added to the fire, swirling around with the orange flames before dying out. Sunset grabbed the Sangheili up by the throat and growled.

"Do it, already... Demon. Do not waste... Hack! ...my time..." Sunset smirked and pummeled the Sangheili, knocking him unconscious. Her rage started dying, and Sunset felt herself seemingly getting shorter. She felt the strength drain from her momentarily, and she stumbled, coughing up smoke. She took a few breaths, her hand holding her up by pushing up to the wall for support.

Flash hesitantly walked over, fear in his eyes.

"Ho-lee-shit, Sunny." Flash applauded, kinda. Sunset had melted a good few centimeters into the floor where her feet left imprints, and her hair felt... longer. She frowned and sighed.

"Magical." Sunset commented with a sarcastic tone. She shouldered her BR55HB and walked around the Sangheili's scorched, unconscious body.

"Why is he still breathing?" Flash asked, prodding it's foot with the barrel of his MA5C.

"Because it'd hurt his honor, and that hurts more than any wounds we can inflict. I do my homework, Major Sentry." Flash rolled his eyes at the comment and started walking down the corridor, alongside Sunset, moving toward the vehicle hangar.

Equestria, 0300 hours, two-and-a-half hours after the theft.

Celestia sat at the desk in her quarters, looking over the magic-made photographs, created from Celestia and Twilight's memory so they may identify the thief while she looked for her crown. She found the photos quite... interesting.

They detail an alicorn, with flame-like wings and a blazing mane that flowed through the air. Her coat was orangish-yellow, with some sort of military uniform on her body, a few strange devices and contraptions on her body. Her eyes were bright cyan, and she had a lot of scars on her face, specifically, a long scar that went across the left side of her head, along with a bad burn scar over her eye that covered some of the upper right section of her face.

Celestia thought back to one of her students... the one that she had failed.

Sunset Shimmer.

Celestia had taken a liking to Sunset from the start, learning her history, albeit dark, and filled with pain. She was an amazing student, always eager to learn... Then she decided to get into the theories of Dark Magic. She would sneak off to the restricted sections, doing Goddess knows what. Celestia found out, and decided it was time Sunset backed off. Sunset was stubborn, though. She kept learning, until she found about that blasted mirror. Celestia, with the assistance of Starswirl The Bearded, had created the portal, for many different reasons she'd long forgotten. When they went through, though...

They found Humanity. There, at the time, was very, very little to go on. They were, in some ways, plenty more advanced than Equestria. They were not in others.

They fought wars against each other, and did some of the most horrific acts Celestia couldn't even think of her ponies remotely thinking of anything like some of the things she'd seen... Not all of them, though, were evil. As long as Celestia, along with Luna and Starswirl ventured at night, they'd be safe.

They helped in modernizing Equestrian ways of life, though, they couldn't be implemented until a good few centuries after Luna had gone mad with power.

In the long run, Celestia should've just destroyed that mirror, but she didn't, and her student was now in that world, very likely dead, or worse... but when Celestia got a look at that alicorn that had stolen Twilight's crown... she saw in those pained, broken eyes...

Sunset Shimmer.

How she became an alicorn was what got to Celestia. She, honest-to-Goddess did not know, but she was back... momentarily, and seemingly in one piece. Celestia wished, with most of her heart, that Sunset would someday return, possibly alive and well...

But she could only wish, at times like these.

Author's Note

For those who want to know, the two-part prologue was only there for context reasons.

A/N:
Sunset's equine form was inspired by this image, that I found browsing on the internet. Picture her like that, or not, doesn't really matter to me.
Here's the link I found attached. Full credit can go to the author.
Also, this chapter, originally was intended to be only a little over a thousand words, and it would've been split up into three separate ones.
Sunset enters the portal>Is in Equestria, grabs crown & leaves>Exits portal.
But I'm lazy, so I just made it like it is.