With Celestia cured and Twilight pardoned, this seems as good a time as ever to change perspective a bit. Consider it a taste of things to come, and an explanation of sorts for things that already have. All of this is happening side-by-side with the story, a parallel drama surrounding a certain blue unicorn and a cross-eyed mailmare.
The Great and Powerful Trixie hauled her new cart through the deep shadows of the Everfree Forest at sunset. The paint on the sides of her magnificent cart was even more elaborate than that on the last cart, and the best part was that it had been free. After a few private shows for the owner of Carts Unlimited and she had had enough blackmail to have the stupid stallion wrapped around her hoof twice. Trixie chuckled to herself about it, and the arrogant azure mare was confidently planning her tour in Hoofington when she heard a soft sound. To an outside observer, the speed with which Trixie was suddenly on top of her cart, with three knives levitating around her would have seemed almost supernatural, though the outside observer would therefore be ignorant of the dangers of this part of the Everfree.
Trixie was cutting through the forest to Hoofington, partially to keep from paying the toll on the bridge, and also to give her arrival an air of mystery. She usually only did that when times were bad, but now with the new cart she simply wished to show off to the ignorant masses she entertained. After several tense moments on top of the cart, Trixie replaced the knives in their invisible sheaths on her back, got down and resumed pulling. She was already considering what tricks she was going to perform, and who she'd try to squeeze for a little extra after, when the whole ground gave way, dropping her and her cart into a deep pit full of some sort of liquid.
“Of all the... The Great and Powerful Trixie is unamused by your prank, whoever you are,” the blue unicorn called out furiously, her voice rolling through the silent forest like an avalanche, “Now come help Trixie out or it shall go hard for you.” The resounding silence that greeted her proclamation started to make the blue mare a little nervous, and she became aware of a ticking noise from nearby. Trixie looked around, and found a curious device wedged into the side of the pit: It looked like a steel wheel with a piece of flint pressed against it, with some sort of clockwork device attached to the side. She blinked, then looked down at the liquid she was in, which was too viscous to be water, and smelled curiously like... Oil. The wheel spun, spraying white-hot sparks down onto the oil moments before Trixie could bring a spell together in her mind to save herself.
A figure a long ways off watched the flames burst from the middle of the Everfree, along the old Hoofington Road, from a hilltop. She nodded in satisfaction as the fire burned, feeling a weight disappear from her shoulders. She'd been careful not to make the pit too shallow, so the trees should be safe from the blaze, but she watched until the fire had extinguished itself entirely, just in case. She stood once the moon had risen and the bulk of the fire seemed to have gone out, and cracked her neck. This mare was also a blue unicorn, but where the one in the wagon had had a beautifully coiffed mane and an arrogant strut in her step, this one seemed smaller, more tired, but with an indefinable toughness about her. Her coat was blue, but patterned with swirls of black dyes that seemed to move as the viewer watched, surrounding her wand and crescent cutie mark and branching out from there like spider webbing. Her eyes were a solid lavender, with no pupils at all, yet she seemed to be able to see fine. Her light blue mane, while more ragged and unkempt, had a sort of artsy style to it nonetheless, and seemed to move of its own accord. Still, even if this other Trixie was more ragged, she might've been sisters with the one that burned with how similar they looked in body shape and bearing. The truth was far stranger.
Ditzy Doo was finishing a last few deliveries in Ponyville when she spotted the strange blue unicorn walking slowly into town. Well, she spotted her when she collided with the ground a little ways away, causing the newcomer to jump and yelp in alarm. “Sorry about that,” Ditzy said, shaking the dirt off her face. She smiled at the blue unicorn, who seemed to be having some trouble deciding where to look. It wasn't entirely surprising, most ponies who make eye-contact with Ditzy for extended periods of time tend to find themselves going very gently cross-eyed as they try to watch both of her wandering eyes at once.
“Uh...” The blue unicorn said uncertainly, “It's okay. Ditzy Doo, right?” At the grey pegasus' enthusiastic nod, the unicorn smiled, “I've heard of you in Hoofington. The only mailmare to make deliveries during tornado season,”
Ditzy puffed up her chest proudly, “That's right! Neither rain nor sleet nor dark of night shall stay this sacred messenger about her business!” She grinned, “Besides, tornadoes are fun, and I've figured out how to keep the mail from escaping... Usually...”
Trixie smiled, relaxing a little, “Well I'm... Trixie, Trixie Sparkle, and I was wondering if you could give me directions.” Ditzy nodded eagerly, “I'm looking for my sister, Twilight.”
Ditzy sat down and frowned, thinking, then tilted her head at Trixie, “Well, she lived in the library over there,” the gray pegasus waved vaguely in the direction of a large tree, “But last I heard she was hanged, then came back to life, and is now on the run for attacking Princess Celestia.”
Trixie blinked, stunned. She'd been out of the loop for a while, stalking her double, learning her habits, but she felt she should've heard of somepony coming back from the dead. The bit about her attacking the Princess though was an obvious fabrication, she felt. Twilight adored Princess Celestia, ever since she'd been accepted to her wretched school, and would sooner chop her own horn off than attack the princess.
Ditzy's eyes regarded Trixie for a moment, then she grinned, “Hey, you wanna come have dinner? You look hungry, and I was about to head home, Dinky and I are gonna make pancakes and muffins!”
“For... Dinner?” Trixie asked, nonplussed.
“Yup! Wanna come?” The grey mailmare smiled at Trixie charmingly, who found herself smiling back, it was impossible to fight the flow of well-wishing coming from this grey pegasus.
Trixie bowed elegantly “I would love to.”
And for those of you curious as to the fate of Applebloom...
In Sweet Apple Acres, Applebloom was sleeping sweetly once more, after being rescued by Twilight from the Beast. She didn't remember much of what had happened, or even how she had been taken, but she remembered Twilight, with her mane burning and shadows leaping from her hooves, carrying her through a nightmare back to reality. Applebloom squirmed slightly in her sleep as the moonlight fell over her, some part of her feeling exposed in the subtle light, a remnant of her violent incarceration.
Slowly, a lock of the yellow filly's red hair started to change color in the light: one of her bangs gently faded to a soft pink. Applebloom stirred in her sleep more restlessly, rolling over as she dreamed about her rescue over and over.
Part Two of Backwards Through the Mirror will come soon, but for now, revisions are incoming for Part One, in between my final projects.