AN: Explanations of the Rangers of Equestria version of Sunset Shimmer. And everyone knows how Equestria Girls turned out anyway so there's no need to rehash those events.
Equestria 101 – Mirror World
"Who's Sunset Shimmer?"
Princess Celestia's eyes unfocused for a moment as she cast her mind back to the time before Shining Light had encompassed every single waking moment of her life and she had a bright and talented unicorn student. She had only just defeated the first uprising of Discord and was rather confused as to what she should have been feeling as the banishment of Luna had still weighed heavy on her mind. It had only been the arrival of Sunset Shimmer that she was able to make sense of the craziness around her. Of course, her student had picked up on her budding infatuation with Shining Light and had teased her mercilessly.
Flashback
"Teacher, you do know that a relationship between two mares is somewhat frowned upon, much less the Ruler of Canterlot and a simple page! I wonder when I'll find the two of you in the hay together,"
Princess Celestia rolled her eyes and looked at her young student, sticking her tongue out in retaliation. Shining Light was a marvellous aide but that was as far as she would allow their relationship to go. After all, Sunset Shimmer was her student and they had a close bond, one that was skirting on the knife edge of gross indecency itself. She had to admit though, there was something about the way the pale amber unicorn tossed her mane around that drew all the stallions to her…or maybe it was how she always had that certain look in her eye that promised both heaven and hell. However, Sunset Shimmer had one glaring flaw she was trying to fix desperately: she had no understanding on the bonds of friendship. She simultaneously cursed and mourned the fact after every lesson as she could see her student had a deep well of potential that would only reveal itself after she had made a friend. Unfortunately, it seemed that all Sunset wanted to do in life was sow chaos with ponies and their feelings.
"Sunset, you know perfectly well I don't have time for any relationships; not when I have you as my student. Although, I have noticed our student-teacher relationship becoming closer than I have ever allowed. Perhaps it is time I changed that and allowed you to enter my chambers on a nightly basis as well…"
Sunset Shimmer's face grew red as her words sunk in and Celestia had to bite the inside of her cheek to keep from laughing out loud. Her student had been mercilessly teasing her for the past few weeks but was easily teased herself and, unless her senses were misleading her again, was becoming excited about any future prospect. As Sunset attempted to stammer out a reply, Celestia's mind turned towards the strange dream that had come to her the previous night. The images she had seen were utterly fantastical and she had cried out in joy at seeing Luna freed from the armour of hate and bitterness that had swallowed her but she knew that they were flights of fancy. Hairless apes walking upright were myths and the thought of super powered warriors was a much needed fantasy. At least Discord had retreated for now but there would be no telling when he would return.
End Flashback
"Sunset Shimmer was my second greatest student. She excelled in all areas concerning magic and she was on the fast track to becoming one of the best minds of all time. I met her soon after the first defeat of Discord, before Shining Light integrated herself into my life. The only issue that arose between us was due to her inability to understand the nature, and magic, of friendship. We grew apart from each other over the decades and, with the benefit of hindsight, I suppose her insatiable thirst for knowledge was what drove her to Discord's second coming. I suppose I should be grateful that, even with all the brainwashing he put her through, she could still come to me and talk about her decision."
Flashback
Princess Celestia looked at the unicorn opposite her and suppressed a sigh of frustration. Sunset Shimmer had not been seen in Canterlot for the past few years but she had suddenly turned up unannounced and asked to have a private discussion with her. They were, ironically enough, seated in the private chambers of the Princess; an amusing fact that was not lost on the young unicorn. Although they had eventually crossed the invisible line of forbidden lust, Sunset had quickly realised that being with another mare was not what she truly desired. She supposed that was when they had begun to grow apart as there was only so much she could be taught without understanding the true value of friendship.
"And you are certain this is the correct path for you?"
Sunset nodded once, her eyes turning down. Discord had shown her many amazing things and Night Shade had fed her hunger for knowledge by teaching her spells to turn heads and enspell minds. He had been in the middle of teaching her a spell to harness her innate powers and transform her mind when she was overcome by a wave of guilt and despair. The black coated unicorn had nodded sagely and had informed Discord with her concerns. Amazingly, the humanoid Alicorn hadn't destroyed her on the spot for daring to have second thoughts; instead, allowing her to have one final conversation with her former teacher to put her doubts to rest. She didn't know what she was doing here anyway; Princess Celestia had finally hooked up with Shining Light, even though she was supposed to be one the Eyes of Discord…or whatever they were calling themselves these days.
Well, that was what she wanted the gullible Princess to believe anyway. In truth, she was here to seek out one of the most powerful artefacts in the Tower: The Mirror of Traverse. What it could do, no one knew but she was damned if she was going to allow its great power to be leeched away by Discord and Night Shade. On one hoof, she would be betraying not only those two but the entirety of Equestria and she would never be allowed to set hoof within the main landmass again. Night Shade had forseen the eventual defeat of Lord Discord and had entrusted her with a mission of utmost importance. Her normal lifespan had been greatly increased by some unknown means and she would continue to live until she was encroaching on the age of ten thousand but that did not matter much to her.
"I am more or less sure of this. Princess, I know this isn't the path you wished me to take and, on some internal level, I understand and apologise. I…I am afraid you will harbour some degree of responsibility on yourself and your actions but, please teacher, don't. I have never ever regretted the years I spent as your student."
Sunset closed her eyes, as if in reflection, but was plotting the next few moments very carefully. Everything needed to be just perfect in order for her ruse to work. Genuinely, she understood the actions of her teacher in the past and knew that what she was doing was gaining the things she wanted the wrong way…but she didn't really care as long as the power was in her hooves.
"Could I, just for old times sake, walk around the Tower? I'll be in direct sight of the guards at all times so they'll know if I wander into places I shouldn't be."
End Flashback
"And you just let her go?"
Princess Celestia shook her head as the Pegasus chariot landed at the Crystal Palace. All seven Rangers and Spike stepped out of the cart and looked around them in awe as the alicorn wondered what her next words were going to be. She had hardly thought anything untoward would happen in the time Sunset Shimmer had asked to look around one last time but, it had seemed, her fears had come true no less than a few minutes later. The Mirror Portal had been accessed by her former student and would not reopen for countless decades and would only resume two-way travel if Sunset returned. As she had, for a very brief time, the Mirror Portal would allow Twilight and one other to safely journey into the world where Sunset Shimmer had made her home for the last few thousand years. Shaking her head, she noticed that the Mirror Portal had been cordoned off from its normal position at the front of the Public Vaults. It was time to act now or else it would be too late for the other world.
"I had no reason to suspect otherwise but this is not the time for such discussions. Twilight Sparkle, as leader of the Power Rangers and the holder of the Element of Magic, I, Princess Celestia, co-ruler of Equestria, charge you with the task of stopping whatever scheme Sunset Shimmer has started. You must pick one other to accompany you as I do now know what dangers await but it cannot be one of your friends as I do not know if the portal can sustain the safe transit of two Rangers."
Twilight nodded once and looked at her faithful assistant. The baby dragon had seen and done so much for them in the past few years but now would be his time to help her in a different way. Levitating the baby dragon onto her back, she separated from the group and strode towards the portal. Allowing herself one quick look back at her friends, who were smiling and waving, she swallowed hard and stepped through the shimmering silver surface. Images rushed out at her and spectres swooped down from impossible angles during the transit, Spike clinging to her back the entire time. She could see flashes of things, of times long gone and futures that would never materialise. She saw herself as an Alicorn facing down a monstrous centaur with upwardly curving horns, each firing off multi-coloured energy blasts. Another group of figures ran down an alley, being chased by creatures that defied all known description, exploding in bursts of light green slime that dissolved anything it touched. When she finally tumbled out into the sunlight, she was a mess. Lifting her arms to her head, she desperately tried to smooth down her hair that had become all tufty in the…portal…wait; she wasn't supposed to have hair.
Swallowing hard again, she looked back to the portal but her vision was cut off as a newspaper smacked into her face. Grumbling under her breath as Spike gawked over his new body, she read the title and frowned in confusion, never knowing her next words would come back to her in the future.
"What's a Kamen Rider?"
TBC…