Into the Past
Queen Opaline was once powerful. The fact she was a Fire Alicorn after spending a decent time as a humble, but no less strong unicorn, should've been enough of a clue to even the most ignorant of Ponies.
Alas, the tyrannical rules of one Princess Twilight Sparkle, the supposed inheritor of the Princesses Celestia and Luna, managed to avert what would've otherwise been an utopian reign under her hoof, and created the Unity Crystals to zap the magic from here, leaving her as a mostly powerless Alicorn.
Granted, she was only powerless by Alicorn standards, but when the only ponies standing against her ascension were Alicorns with all the powers included... that was kind of a big deal.
Luckily, she had a contingency plan.
"Queen Opaline, I found it!"
The Fire Alicorn turned around to see a Unicorn with a light blue coat and a dark blue mane approaching her, drenched in water while using her magic to levitate a scroll inside a bottle.
"Excellent! After eons lost to time, the spell has finally been retrieved!" Opaline proclaimed as she took over the levitating and opened the bottle.
"Yeah, though to be fair, it was surprisingly easier than I expected," the unicorn remarked as Opaline took out the scroll. "Sure, it was surrounded by a bunch of water, which would be terrible, except it was inside a bottle so there was no risk of it getting wet and being subsequently ruined. Though now that I mention it, why would somebody place a super important spell like this inside a bottle? If they didn't want it to ever be used again, for whatever reason, they could've just destroyed it, right? I mean-"
"MISTY!"
Opaline's thunderous shout echoed across her chambers, causing the unicorn to suddenly go quiet before Opaline sighed:
"I can't concentrate on my evil scheme if you're rattling and prattling like crazy! So please, don't speak again until after I've finished
The unicorn looked around. "Can I at least ask what your plan is?"
"Ohoho, silly Misty, don't you know?" Opaline shook her head. "It's been proven time and time again that any plan that is revealed without being near completed is doomed to fail! I mean, why else do you think that those other losers like, King Sombra, or Queen Chrysalis, or Tirek, or whoever was the other one, why do you think their plans failed?"
Misty paused. "Because they were confronted and defeated by the Elements and Guardians of Harmony? Mostly Twilight Sparkle?"
"Ha! You're wrong on both fronts!" Opaline responded. "Not only were they NOT defeated because of the Guardians of Harmony, but Twilight wasn't the sole one to defeat them! There was another!"
Misty's eyes widened. "Whoa! Who was it?"
"The same pony who created this spell!"
Opaline placed the scroll on the ground before generating energy from her horn, which she used to create the image of a light purple pony, sporting blue eyes and a dark purple mane with turquoise highlights.
"Starlight Glimmer!"
"Ooh..." Misty blinked twice. "I've never heard about her, though. Neither from you nor anybody else."
"Of course you didn't," Opaline scoffed as she dematerialized the image. "Unlike a certain spoiled princess, Starlight Glimmer was more than happy to be left forgotten by the trials of time, being left as nothing more than a simple easter egg to be uncovered by those historians crazy enough to try find the truth regarding the history of Equestria."
Then, she looked back at the scroll. "But enough talk!"
Opaline's horn glowed, and she unrolled the paper to unveil the instructions.
"It's time to unleash magic that hasn't been seen in eons!"
And so, once she read the instructions, Opaline's horn glowed before she released a blast of magical energy, opening a portal on the sky that glowed as it spread until it was big enough to engulf her.
"Huh, that was... surprisingly easier than I expected. But then again, Starlight Glimmer had almost everything handed to her in a silver platter, so I guess it makes sense that her own spells wouldn't be complicated."
Opaline flew towards the portal, and the scroll flew over to Misty, with it landing right on her face. However, this proved to be a good thing, since it allowed the unicorn to spot a peculiar passage...
"Queen Opaline, wait!" Misty gasped. "I think there's something off about this-"
"Can't hear you, Misty!" Opaline chuckled as she flew up. "I'm about to head to the past like a certain samurai from ancient times! What was her name, Applejack? Yeah, Applejack."
"B-But it says here that using this spell might bring unintended side effects!" Misty cried.
"Bah, that's nothing more than hogwash to make anybody brave enough to find this get cold feet in regards to using it!" Opaline chuckled. "Now, if you excuse me, I gotta rewrite history!"
"Opaline! Wait!"
But it was too late: Queen Opaline entered the portal moments later, with the portal outright sucking her in as a white flash of light engulfed the castle, leaving Misty all alone with the scroll, which began to disolve as soon as she turned to look at it.
"Oh no! Nonononono!"
Misty tried to fix the vanishing scroll, but it was for naught: the papers ceased to exist right in front of her eyes, and looking at the spot where the portal once existed, she said with a sad look on her face:
"Please be safe, Queen Opaline..."
...
Speaking of Opaline, the dark purple pony found herself falling from a decent height on the other end of the portal, with her screaming until she hit the ground. Luckily, her Alicorn strength allowed her to survive the fall; it would've been a very messy fall otherwise.
Yup, that was totally the reason.
When Opaline stood up and opened her eyes again, she found herself in the middle of some village she didn't quite recognize. However, she had landed in front of one house she did recognize: the house belonging to Starlight Glimmer's family.
"Eureka! I've managed to travel back in time!" Opaline chirped aloud. "But how long back did I travel, is the real question here?"
It was then that the door to the house opened, and from there emerged a colt with an orange coat with white hooves, and dark orange hair. He left the house looking rather sadly, a sight that, morbidly enough, brought a smile to Opaline's face.
"Looks like I arrived just in time!"
Opaline trotted right into the house right before the door was closed, with her facing very little opposition as she headed towards a younger Starlight, who was crying next to a broken game.
"Greetings, Sta... I mean, fellow pony!"
Starlight raised her head, tears streaming down her cheeks as Opaline proclaimed:
"My name is Opaline, a Fire Alicorn from the future who has come back to steer your life in the right direction! Now tell me, would you like to join me in creating a plan to ensure we create an utopia that will continue eons into the future?!"
Starlight wiped the tears off her cheeks. "Fire Alicorn? What are you talking about? You look like an ordinary unicorn to me."
Opaline paused. "Come again?"
"Yeah, you have the horn, but you don't have the wings, which is kinda what separates an alicorn from an unicorn. At least, that's what Dad told me," Starlight answered. "You're not even that much bigger than me, you don't look older than me even!"
Opaline's eyes widened, and she ran to the nearest mirror available, which showed her as a young filly with an ordinary horn, and no wings, though her coat, mane, and eye color remained exactly the same. And as she processed what this could possibly mean, Opaline gasped:
"What in the name of me, myself, and I?!"