Twilight Sparkle trotted carefully as she traversed the Everfree Forest, keeping an eye on her surroundings while she followed a crudely drawn map, courtesy of Pinkie Pie. Even though the Everfree Forest was mostly safe during the day, Twilight was taking no chances when it came to the forest after her various and dangerous encounters with the wildlife.
Twilight winced as a gnarled branch that escaped her vision scraped against her side, leaving a dark red welt that she would probably feel the next day. While her destination wasn’t the easiest or the safest to get to, the lure of forgotten knowledge and accomplishment was too tempting to pass up.
Soon enough, Twilight approached an inconspicuous grey large boulder with its bottom half lodged deeply into the ground. She triple checked the map, seeing if she followed all the landmarks in order and was truly at her destination. Satisfied that this was the right rock, she effortlessly encased the rock in a magical glow and lifted it off the ground.
Twilight carefully placed the boulder to the side of the hole it revealed. The boulder shifted as it was lowered onto the flat ground, but quickly stabilized and lay still with the force of its own weight and the watchful eye of the unicorn.
Rarity wouldn't be happy if I lost Tom. Twilight thought to herself with amusement as she entered the hole the boulder was covering. While the marshmallow colored fashionista insisted that she never wanted to see that dreadful boulder ever again, Twilight knew that the boulder served as a reminder and a symbol of how it was to be opposite of your true self and while unsaid, drove the fashionista to be all the more true to herself and her element of Generosity.
Twilight shook her head. Now wasn't the time to be reminiscing about her friends who were safe in Ponyville doing their daily jobs if she wanted to be back home before night fell and the forest became too dangerous to travel, especially alone and through a forgotten path through the forest.
The purple unicorn peered into the dark hole, and lowered her head as she concentrated. In response, her horn lit up with a brilliant light as she carefully lowered herself into the hole and into a dirt tunnel sloping downwards into the earth.
The dirt walls and floor near the entrance of the tunnel quickly melded into smooth rock as the unicorn traversed the straight tunnel and descended further and further. Soon enough, the tunnel opened into the upper wall of the cavern that lay at the end.
The cavern shone with an mysterious beauty that took Twilight's breath away as she entered the room. The tunnel she just exited from sloped downwards to the center of the cave, where a perfectly circular pool of water was formed with a tiny stream keeping the pool filled with water. Various plants and fungi grew on the walls and ground, and many glowed with an ethereal light, giving light to the blue rock the cave was made out of. A spot of sunlight also entered the cave through a small crack in the ceiling, illuminating the pool of water in a pillar of light, leading for the cave to have an almost alien look to it.
Twilight slowly stepped down to the pool of water, careful not to lose her step due to the slightly steep slope that curved its way down to the main portion of the cave, and stared deeply into the unmoving crystal clear water as if searching the water for something visible. The pool responded by rippling slightly by the disturbance of air caused by her sigh before being still as a statue again.
While the pool looked harmless, Twilight knew, it was a dangerous artifact that was remnant of the ancient times where there was no laws or limits on magic usage. The pool was named the Mirror Pool by Starswirl the Bearded, the pony to rediscover the magical pool after he concluded it was lost for centuries after various magical tests of the rock surrounding the cave and the water itself.
The pool was named as such due to its property of creating a magical construct of the pony who walked in (despite what a certain pink pony said, there was no need for magic words to activate it). While the magic created to clone the user was a success, the clone was only a shallow copy of the original, with no memories or a full personality but many of the skills the original had.
Accounts from friends of Starswirl the Bearded said that the archmage tried to dissipate the magic working the Mirror Pool and deemed it too dangerous due to the amount of magic that was stored and accumulated over the centuries it was hidden (it is also said he forgot the exact location of the pool and therefore never could return to destroy it but made a theoretical counter-spell in case someone did find it and abuse it).
While Twilight respected her idol of magic on many things, she disagreed that the Mirror Pool couldn't be destroyed without danger to the environment or to the ponies who were trying to drain the magic.
Twilight opened her saddlebags that she was carrying with a glow of purple magic and pulled out some folded scientific instruments, a piece of parchment and a quill, and a book. Opening the book to the correct page that she memorized the day before, she began to read the page detailing Starswirl's notes on the Mirror Pool for the tenth time, memorizing his figures and equations for the pool yet again.
Twilight unfolded the first instrument, shaped like a long grey rod with one end larger than the other and had carefully inscribed markings that looped around the rod in exact intervals. Channeling her magic, she carefully dipped the smaller end of the rod into the water, making sure not to activate the magic stored within and watched as the rod slowly began to glow a blue color.
The blue slowly started to spread to the larger portion of the rod as it absorbed more magic from the pool. Soon enough, it filled the whole rod and Twilight frowned at the result. Taking a bigger rod that she took just in case, and dipped it in the pool more impatiently than the last. Like the previous rod, it was not long before the whole rod glowed a bright blue color.
Twilight frantically scribbled notes and equations on the piece of parchment she had in front of her and her brow furrowed further as she kept coming to a conclusion that was illogical.
Finally, she conceded defeat and sat down on her haunches, frowning at the problem before her. While she considered it a small pride that she just proved one of the greatest archmages was wrong in his calculations, the Mirror Pool was not smaller than when Starswirl measured it. In fact, it was at least two times as large as he calculated and was probably much more due to the fact that she didn’t have a bigger measuring rod.
Twilight sighed, her breath causing tiny ripples to shoot across the small pond. She knew that it was a futile and probably deadly task for her to try to dissipate the magic by herself with the amount of magic it had.
Biting her lower lip, Twilight made a few quick calculations in her mind. She needed to figure out the amount of magic stored in the pool, but without the tools on her, it would be a time consuming journey. If she didn't take all the measurements now, she wouldn't have time in her planned schedule to come back for another month. It was unacceptable to her to leave research unfinished as much as it was unacceptable to not finish a good book.
Closing her eyes, she channeled her magic again preparing to test the magic of the pool, but this time with her own magic. While more risky to herself if she accidentally activated the magic and caused backlash, the potential reward was more than worth the risk. She leaned forward, her head nearing the water as her magic spread across the pool's surface carefully probing the magic reserves of the pool itself.
As she lowered her head, movement appeared from the corner of her eyes. Her heart beat faster as she scanned the room, looking for the source. Finding nothing seemingly disturbed, she took a deep breath, trying to calm her nerves. The once majestic cavern now seemed far more ominous than before, especially when her brain helpfully reminded her that she was still in the Everfree Forest.
Twilight once again faced the still water, channeled her magic, and leaned forward far faster than what most would consider safe.
But what Twilight didn't know was that the Mirror Pool started as a pony sized pool. As the pool was abandoned and fell into disuse, it could not hold all the magic it was gathering to create the clones and so dissipated the rock around it to make more room for the magic that kept accumulating. This made the rock around it slowly weaker and weaker as it accumulated more and more magic.
Unfortunately for Twilight, the rock around and under one of her front hooves decided to crumble to dust at that exact moment and she toppled headfirst into the pool before she could think to yelp. Her horn touched the pool, still glowing with magic, and Twilight felt a burning pain in her horn as the pool’s magic tried to expel the foreign magic.
The last thing Twilight remembered was the distinct feeling of cold liquid running over her body before the feeling of endless falling into darkness as the world faded from her view.