Author Note: This story features another character of mine from a different story. Reading that is not a requirement for this story

Starlight Glimmer was starting to panic.

Scratch that, she was way past the point of panic, and approaching a full on mental break down. Princess Twilight Sparkle and her friends, the Elements of Harmony, had been missing for almost a month now. Normally, this would be classified as A Very Big Deal, but these were not normal times. Everfree Forest had grown even more wild and chaotic and was once again encroaching on the outer limits of Ponyville. The monsters that lived deep within the forest began to stir and waken, causing trouble for everypony. The weather had become very unstable, forcing Cloudsdale and the all of the Pegasai to work frantically around the clock to prevent one disaster after another. Contact with the Crystal Empire, difficult in the best of times, was virtually impossible. A raging snowstorm howled night and day through the north. Griffonstone had ceased all contact, nopony had heard from Mount Aris, the Dragons became more hostile, and the yaks had retreated to bolster their own border.

The biggest change, was Princess Celestia. The monarch of the Sun, normally poised and in control of her emotions, had become erratic and unstable. She re-instated the draft of all military aged ponies, mares and stallions alike, and called up reserve units to active duty. The Wonderbolts, Equestria's premier flight squad was reassigned to combat air patrols over Equestrian airspace. The Canterlot police force had tripled in size to accommodate the increased patrol rotation. Scouts were sent to beef up border security.

During this time of suspicion and unrest, Twilight's Friendship School was closed and the students returned to their respective countries. To Starlight's dismay, the order had come from Celestia herself, saying everypony should stay with their own kind. This blatant racism was a slap in the face to everything Twilight stood for, and Starlight was secretly glad the Princess of Friendship wasn't around to see this. Princess Luna, despite her best effort, was largely ineffective in her attempts to curtail Celestia's actions. The lunar princess spent most of her time trying to keep the kingdom from falling apart. Discord was nowhere to be found, having disappeared after Fluttershy went missing.

Starlight had practically worn a circle in the crystal floors with her worried pacing. Spike had gone with Twilight and the others, leaving her all alone in the big castle. Trixie stayed for a little while to keep her company, but ended up leaving. She said it was to go out and spread cheer to other ponies in this sad time, but Starlight suspected Trixie wanted to get as far away from Ponyville as possible. She didn't blame her friend. Starlight wanted to leave as well, but what would that solve?

Starlight was so caught up in her worries that she didn't see the mirror portal come to life. Bright flashes appeared in the mirror and a familiar pony with a red and gold mane stepped through.

The first thing Sunset Shimmer saw was Starlight Glimmer pacing nervously back and forth. Her coat had lost its luster and her mane was a tangled mess. Sunset saw the dark circles under Starlight's eyes and wondered how she was keeping it all together. "Starlight?" Sunset cautiously called out.

Snapped out of her thoughts, Starlight looked up and relief flooded her face. She practically threw herself at Sunset, who gaped in surprise and stumbled to prevent falling over. "You came! You actually came!" Starlight cried.

"Of course," Sunset replied, clearly confused. "Why wouldn't I?" She pushed Starlight away and took a good look at the teary unicorn. "Starlight what happened? Where is Twilight?"

Starlight sniffed. "You better come with me," she said. Frowning, Sunset followed behind. Thinking back, Sunset found it strange that Starlight Glimmer had started writing in the journal. The entries had started out a bit odd and quickly devolved into pleas for assistance. The final straw for Sunset was a single word scrawled across two journal pages:

HELP

Starlight sat at the table and slumped over, looking completely defeated. They hadn't really had a chance to talk and get to know each other, and everything Sunset knew of Starlight came from Twilight. Sunset knew Starlight as a smart and very capable unicorn, and seeing her in this state caused her to worry even more. "What happened here?" she asked.

Starlight looked to Sunset with confusion. "Didn't you read the journal entries I sent?" she asked.

"I did," Sunset nodded, "but most of them didn't make any sense." Sunset reached into her saddle bag and pulled out her journal. "'Hello Sunset Shimmer, this is Twilight Glimmer. I know we don't know each other very well, but have you seen Twilight? Has she gone to visit you?'" Sunset turned a few pages. "'Sunset, it's Starlight. Are you sure Twilight isn't with you?' It goes on and on and ends with this." Sunset turned the journal and showed Starlight the last entry. "Why is Twilight missing?"

"I wish I knew!" Starlight exploded in frustration. She then looked down at her hooves, embarrassed by her outburst. Sunset was momentarily stunned, then moved next to Starlight and embraced her in a big hug. Starlight grabbed her tightly and tears flowed freely down her face. "Starlight, I can't help you if I don't know what's going on," Sunset whispered in her ear.

Starlight let out a big sigh and leaned back. "I'm sorry." She smoothed her mane back and cleared her throat. "I guess you could say it started when Celestia publicly executed this strange looking bipedal creature."

Sunset heard what Starlight said and it took a second for it to sink in.

When she finally comprehended what was said, her mind went blank.

has stopped functioning. Re-boot? Y/N

Y.

Re-boot in progress.

Re-boot complete. unexpectedly shut down. Re-open previous thought? Y/N

Y.

Previous thought re-opened.

"WHAT?!" Sunset shrieked.

Starlight recoiled at Sunset's outburst. "After that, Princess Celestia has been acting more and more out of character. It's almost like the Princess thinks this is the early days of Equestria when everypony was fighting with everypony else."

"Stop, stop, stop," Sunset quickly interrupted, waving her hooves in the air. "Go back to that earlier part. You said Princess Celestia executed somepony?"

"And publicly too," Starlight added. "The whole thing was odd from the start. Celestia claimed the creature had snuck into Equestria to cause mayhem and destruction. To top it all off, Celestia accused the creature of killing Lord Tirek."

Sunset's brain suffered another reboot. "WHAT?!" she shrieked again.

Starlight narrowed her eyes and slowly sipped her tea. "Really? You should learn to control you outbursts."

"Oh that's rich, coming from you," Sunset said angrily. "Three seconds ago you were a hot mess, clinging to me like your life depended on it."

"And it still might," Starlight added. Sunset smacked herself in the face with her hoof. This was definitely not what she was expecting when hurried through the mirror. Whether it was Sunset's presence or the tea, Starlight seemed to have regained some measure of her composure. "Also, I think the castle is haunted now," Starlight added matter-of-factly.

"Of course it is!" Sunset exasperated, throwing her hooves in the air and falling backwards out of her chair. As she lay there on the floor staring up at the ceiling, Sunset tried to figure out what to do next. "Oh, and you still haven't told me what happened to Twilight and the others," she said.

Starlight hummed to herself and furrowed her brow in thought. "About a week or so after the execution, Princess Celestia summoned Twilight and the others to Canterlot. As it turns out, the unrest and bad things Celestia had warned us about were happening much faster than anticipated. She told them the source of everything was deep in Tartarus. And so Twilight led her friends on a journey to the depths of Tartarus, on the orders of Celestia herself." Starlight took another sip of her tea. "They haven't been seen since."

"Hmm," Sunset thought out loud. "Did anypony actually see them enter Tartarus?"

"Of course. Celestia was there to wish them luck, along with some of her guards," Starlight replied.

Sunset looked to Starlight from where she was on the floor. "And where were you during all of this?" she asked.

"Here in the castle, trying to keep everything from falling apart. For all the good THAT did me," Starlight grumped.

When Sunset gave her a questioning look, Starlight continued. "You see, since Twilight is the Princess of Friendship, Savior of Equestria and all, that means she's constantly called away. And that means leaving me in charge of her school. And naturally, when Twilight goes anywhere, some, if not all, of Twilight's friends accompany her. And guess who happens to be instructors at this school? If you guessed the Bearers of Harmony, then congratulations, you win the jackpot!" Starlight was huffing angrily at the end of her little rant.

"Wow. Tell me how you really feel," Sunset replied sarcastically.

Starlight let out a sigh and rubbed her temples. "Look. It's not that I dislike Twilight and her friends. I am grateful that Twilight basically risked the end of Equestria to show me that I was wrong. I just can't help but feel that none of them take any of this seriously. I mean, Twilight is in charge of AN ENTIRE BUCKING SCHOOL FOR CRYING OUT LOUD!"

Starlight hopped out of her chair and stood over Sunset. "I mean, do any of them actually think any of this through? It completely baffles my mind that all of them have normal lives, in addition to being the Elements of Harmony. How do any of them have time to manage any of this? How is Rarity's boutique still in business? How has Fluttershy not been locked up for animal abuse? Pinkie needs no explanation."

"Wow. You're really worked up about this," Sunset said and picked herself up off the floor. Starlight was still unhappy, but at least neither of them were shouting anymore. "Okay. I feel like we've gotten off topic here," she added.

Starlight's anger melted away and she lowered her gaze to the floor. "You're right. I'm sorry. I asked you for help and so far, all I've done is cry and complain about everything."

Sunset smiled and gave Starlight a pat on the shoulder. "Don't worry about it. If there's one thing I've learned, it's that sometimes you just need to vent to a sympathetic ear."

Starlight let out a small chuckle. "I suppose you're right. It is nice to have sompony to talk to about all this. Twilight doesn't really get it."

"Perhaps it's because she's always been a slightly neurotic goody-two shoes, whereas we are former villains of the highest order," Sunset offered.

Starlight shot Sunset a sly grin. "Perhaps. Speaking of which, who decided it was a good idea for two baddies to have complete run of the castle?"

Sunset found herself amused by Starlight's proposal. "As much fun as that would be, I think it would be best if we focused on our main problem."

Starlight frowned and sat on the floor. "I've already driven myself crazy over this. Any ideas?"

Sunset frowned and tapped her chin in thought. "You said something about the castle being haunted now?"

"Ah! Yes I did," Starlight nodded.

"What proof do you have?" Sunset asked.

"For starters, I've only noticed it at night," Starlight began.

"Because of course," Sunset interrupted.

Starlight glared at her before continuing. "I think it would be quicker to just show you," she said and set off with Sunset following behind. As Starlight led her through the castle, Sunset began to appreciate just how big it actually was. "Wow. This place is so much bigger than it looks."

"That's funny. Dr. Hooves said the same thing," Starlight said. She finally stopped before a simple wooden door with a single key lock. Starlight's horn flared to life as she began to manipulate the lock.

Sunset watched for a few moments and said, "Wouldn't it be easier to use the key?"

"This is Twilight's research room. She has the only key," Starlight said simply.

Sunset narrowed her eyes. "And you don't think she would have warded the lock to prevent you from doing exactly what you are doing?"

"Twilight is a genius, but that doesn't mean she's smart," Starlight said. "Of course she warded the lock, but getting past it is easy when you know she used Keep Out, Keep Away, instead of Lock Tight."

Sunset considered this, and realized it made a bit of sense. "Well in that case, by all means, continue breaking into a Princess's private study."

Starlight winked and made a face at Sunset. "Reformed baddie, remember?"

Sunset rolled her eyes and Starlight finished picking the lock. She pushed the door open and cast an illumination spell to light the room. Sunset stepped inside and looked around in awe. "For some reason, this is exactly how I imagined it," she said as she casually browsed through the room. She stopped and read the titles of a few books. "Oh. So that's what happened with 'Of Mice and Magic Volume IV.'"

Starlight scoffed and rolled her eyes. "Of course little miss Princess of Friendship would keep all of the best books and scrolls to herself. But that's not the best part." She then showed Sunset the desk in the middle of the room. A thick manual lay open on top and Sunset hopped up into the chair to read it. She frowned as she browsed the pages.

"When she's not on an adventure or saving Equestria, Twilight spends most of her time holed up in here studying that book," Starlight said. She then pointed to a large chalkboard covered in scribbles and equations. "I mean sure, light speed travel is cool and all, but what's the point if you can't actually make it work?"

At this, a memory bubbled up in Sunset's brain. Her eyes went wide and she quickly closed the book to the front cover. Sure enough, she recognized what it was. "I know what this is," she said.

"Besides a book on space flight and near-light speed travel?" Starlight offered.

"Sure, but that's only part of it," Sunset said. "More importantly, this book comes from an alternate reality!"

Now it was Starlight's turn to be confused. "Wait. Stop. Hold up. What do you mean? How would you know that?"

"Because I know the person that gave it to her," Sunset replied sheepishly.

Starlight's eyes slowly grew until they were the size of dinner plates. "You. And me. Are going to have a little chat when this is over," she said, quite seriously.

Sunset smiled and nodded in reply, then became serious again. "So this ghost?"

"Right," Starlight said, getting back to the point. "At first it was small things. Books were switched around or misplaced. A book would disappear on night, then show up in a completely different room later."

Sunset frowned. "Is there some kind of pattern to the missing books?"

"At first I didn't think so, but after a while I noticed a theme," Starlight said and erased a corner of the chalkboard. "The first few book were on the history of this world and the founding of Equestria. Then an entire section of Starswirl's spell books went missing, followed by Clover the Clever's journals on Magic theory and application. Lately, the ghost has taken an interest in biographies of Princess Celestia."

As Sunset thought about this, Starlight went to a corner and pulled out a small table. "Then one night, this appeared. I haven't had the chance to look into it yet."

Sunset's eyes went wide. The object in question was a metal square with what looked like a red square-cut gem in the center. Two rings, an inner and outer were mounted to the square. Six metal fins were mounted to the outer circle, three on each side. The whole thing looked like a fancy gyroscope, but Sunset suspected it did more than just measure angular momentum. She quickly tore through the pages of the book, until she found what she was looking for. "Starlight, come look at this," she said.

Frowning, Starlight hopped up on the chair next to Sunset and looked where she was pointing. Her eyes scanned the pages and Sunset watched with some satisfaction as realization lit up Starlight's eyes. She looked up at Sunset in awe. "I think our mysterious ghost is a traveler from a different world," Sunset said.

"But…how is that possible?" Starlight sputtered. "There's only one mirror portal, and that's the one here in the castle. Right?"

Sunset frowned. "Apparently not."

Starlight jumped down and began pacing in circles. "So does that mean Celestia was right? A bipedal being from another world came here to cause trouble? But Celestia killed it right?"

Sunset stared at the NLS drive sitting innocently in Twilight's study. "If what I know is true, then Celestia has made HUGE mistake, and she doesn't even know it yet." Fearing the worst, Sunset asked, "The creature that was executed. Do you know what it looked like?"

Starlight thought for a moment and shook her head. "I was stuck here in Ponyville during the execution. However, I did hear that the creature looked like a human with blue skin."

A wave of relief washed over Sunset. She didn't think that Celestia had executed Hildr, but it was the only thing that made sense. But there was another, or at least appeared to be. This thought cause Sunset to jolt with surprise. Did this mean that there were Vex portals active in this Equestria as well? Sunset fought a wave of panic. If that was true, at least she knew how to stop them.