Moondancer's misguided mission

Flashback

The mists within the glass orb began to swirl, and a picture slowly began to form. From the haze emerged the vision of a white, rainbow maned alicorn, standing over a yellow unicorn filly with a fiery mane, and a Burning sun cutie mark.

"Thait looks just like Sun Shimmah!"  Truly exclaimed. "Ahnd she's with Princess Celestiah?!?"

"Shhhh! I want to hear this!" Moondancer whispered, looking back into the orb.

"Young Sunset Shimmer, I am very pleased that you have decided to become my personal student." The Princess announced proudly. "I hope to pass on to you everything I know about magic."

"Thank you so very much, Princess!" The little filly replied enthusiastically, bowing to her new teacher. "I promise that I won't let you down!"

"Why aren't their lips matching what they're saying?" Zigzag asked curiously.

"Because the spell is translating their words into english, and it's not an exact translation." Moondancer replied. "Now will you please let me listen?"

The images moved forward in time, and the there observing equines saw Sunset grow before their very eyes, growing stronger and stronger in magic each day under Celestia's tutelage. Finally, an angry-looking Shimmer stood before the alicorn princess defiantly.

"Why haven't you haven't taught me everything you know?!?" Sunset demanded. "I want to be stronger!"

"Magic isn't just about strength." Celestia replied sadly. "I had hoped you would have learned that by now."

"The only thing I've learned is I'm done with being your student!" The defiant filly yelled, running out of the throne room. "I'm gonna become the most powerful unicorn that ever lived! I'll even become more powerful than you!"

"Why that ungrateful little tramp!" Moondancer snorted. "How dare she talk to the princess that way!"

"Vould you please be qvuiet, Moondancer?" Gypsy snapped. "Ve are trying listen to ze converzation!"

It was at that point that Sunset Shimmer began looking through books in the Royal library, and using that knowledge, found a mirror hidden away deep in the castle, which the arrogant unicorn filly stepped through... and she was transformed!

"By ze horzemazter!" Gypsy exclaimed. "Zhe haz become a human!"

"Shhhhhh!" The other three exclaimed simultaneously.

"This world is incredible!" The newly humanized pony exclaimed. "Here I shall go stronger, and when the time is right, all of Equestria shall be mine!"

The images shifted again, and the girls saw Sunset Shimmer worm her way into a human high school. They saw her manipulate the other students and tear friendships apart, and take over the school in a remarkably short amount of time.

"Wow,  she shore iz doin' a good jawb a makin those young'uns lives miserable!" Truly snorted.

"Moondancer, how can this be?!?" Zigzag asked in shock. "That was the human world she was in, how is that possible? That world was in it's Middle ages when Equestria was in it's golden age!"

"I believe I know what going on here. I don't think this is Megan's earth we're looking at here." Moondancer replied, staring at the crystal ball knowingly.  In my magic studies, I had heard of a world on the other side of the mirror, where human versions of all the ponies of this world exist. The humans counterparts in this mirror world have pastel skin colors and shades of hair you'd never see on one of our humans. It's not a parallel world, merely a reflection of our own, on the other side of the mirror."

The ponies then saw Twilight Sparkle arrive in that world, and battle and defeat Sunset Shimmer in a struggle for her crown, which the evil filly had stolen. Twilight befriended the human versions of her friends, then undid Shimmer’s damage to their friendships/ The humanized alicorn princess overcame Sunset, with the undefeatable power of friendship. A repentant Sunset remained in the human world, even as Twilight made her way back home.

"So Sunset Remained beahind, afta turnin' good." Truly noted. "But haow is she in Dream Valley naow, makin' all our friends tuhn evil?"

"I don't think she is, Truly." Moondancer replied, watching the events in the globe unfold. "She tried to make friends with the girls in that world, but their was always a distance between them and her, after what she had done."

The visions shifted again, and they saw Sunset sadly going back through the portal, returning home several years after first coming to the mirror world. But when she had come through, Sunset found a different world than the one she had left.

"W-what's happened to Equestria?!?" A hysterical Sunset screamed, looking around at the ruins of Canterlot. "What happened to my friends, my family?!?"

"So that's how she got to the present!" Zigzag noted knowingly, nodding. "The flow of time difference between the two worlds, must have changed between portal openings."

"This is all Twilight Sparkle's fault!" Sunset Shimmer growled, as she wandered the countryside alone. "I'll never see the world I knew again because of her!"

They watched the filly make her way across the pony communities, from Fort Rainbow Dash to Hoofkaido, playing the part of a simple-minded fool. Eventually she caught the eye of a Stallion, as bitter and angry as herself, and one lifebond later a young unicorn foal was born to them. They saw the filly reach childhood, as the mother trained her to be the living weapon the baby had been birthed to be.

"This is a mind manipulation spell, Sun. while not as good as mind control, it'll allow you to cloud a pony's judgment, making them more susceptible to any radical suggestion you might make."

"No! Don't wanna learn magic!" The filly protested. "Wanna go out and play!"

"NO!" The older mare screeched, smacking the toddler across the mouth, and knocking her to the ground. "You're not going anywhere until you learn the weakest version of this spell!"

"O-okay..." The little filly whimpered, wiping the trickle of blood from her mouth with her hoof. "I'll try harder, I promise..."

"You need to become the best, like I was." The mare snarled, as the four equines watched the little filly grow up with the unhappiest of childhoods. "If your going to Punish ponykind, and destroy Dream Valley- Twilight's Sparkle's legacy- you need to become the best."

The mists swirled again, and they saw a fully grown Sunset Shimmer, standing before her mother's tombstone, her eyes burning with the utter hatred and coldness her upbringing had instilled in her.

"You'll need to be the best, if you are to carry out my revenge."

As the mists in the crystal ball cleared, the four mares only sat there, staring at each other in silence.