Thankfully, I already don't remember this, Tia!
I know I enjoy learning about things, it's just who I am! Knowledge, glorious knowledge, from everything and everypony! Sometimes they're not even ponies, but it's knowledge! Books, movies, newspapers, even that ad for plushies of me and my friends which I found to be slightly off detail of us! There is a lot of knowledge, and I love it! Which is why I'm near killing myself now by thinking this; I wish I DIDN'T know about this!
Twilight Sparkle was currently with Celestia and Chrysalis in the royal library, and the topic that they were discussing was magic. While the unicorn was skeptical about having Chrysalis over, she realized that it would do no good to hold a grudge against her since she was now an official princess, and, in hindsight, she did ruin a good prank played on Cadence's wedding. So all was said and forgiven, though Twilight was still a bit wary of Chrysalis.
"You're telling me that you can do that?!"
The question was directed at Chrysalis, who nodded slowly. "Yes, it is a very powerful spell, but it is by no means perfect. Here, this is how it's done." Chrysalis levitated over some parchment where she began to write down the mechanics of the spell to a powerful if limited memory control spell. It was, however, not very practical, as Twilight saw from the notes that Chrysalis was jotting down. Beside Twilight, Celestia was raising a brow, concerned about what she was seeing.
"Chrys, is this spell really safe for Twilight to learn? From what I can tell so far from what you've written down, it uses a lot of energy, goes off with a bang, and can cause permanent damage if not used correctly."
"It's perfectly fine, Tia." Chrysalis continued to scribble her notes about the spell down, making sure to jot down even the most minor effects the spell could do; after all, spellcasting was never a perfect process, and spells were constantly wired and rewired to either put less strain on the unicorn (or alicorn), work more efficiently, or even perform a different task entirely. "It's just that this spell isn't wired to be the most efficient or safe thing around, as it was something I made up on the spot."
That was horrifying to Twilight. "You used an untested spell on my brother?!"
Chrysalis groaned, and set down the quill to look at the unicorn dead in the eyes. "Of course not! What do you take me for, a mad scientist?! I would never do something that would endanger a pony or changeling's life! I admit, my wording was not the best there, but I assure you it was not 'completely' made up on the spot. I simply took the idea of existing spells that dealt with memories and took only the good bits of wiring and combined them together in a logical if somewhat impractical manner. The result was a power memory control spell that made it possible to plant false memories into a pony's mind, though constant use of this spell did, as you saw, cause Shining Armor headaches. In any case, I'm done, I believe I've outlined the general spell as well as any effects you might have; I'm the only one to have cast this spell, so it might be different for you, no matter how powerful you are, Twilight."
Twilight looked down at the notes Chrysalis had, and frowned as she saw the intricate yet seemingly simple framework of the spell. "This is...How did you even manage to get the spell to work within these limitations, Princess Chrysalis?"
Being called princess by a pony that had learned to say her mentor's name without adding the title to it somewhat irked Chrysalis. "Please, Twilight, just Chrys will do. The reason why the spell even works with its obvious faults right now is because of the fact that I channel the spell over a long period of time; it's not meant for an immediate 'now' result like most unicorn magic is. Most changelings don't have the magic power to instantly get results like that, so we tend to use spells that work over a period of time; it's more time consuming, but we get just as good results as if we instantly made it so."
"I see...Interesting." Twilight continued to study the notes for a little while longer, the beginnings of a new system creeping up inside her thought process. She levitated over a new piece of parchment and the quill that Chrysalis set down, then began to rewrite the spell. "The problem with this spell is that it is completely impractical to anypony or changeling because of the massive power required that very few unicorns or changelings would be able to output over the course of your written 'safe-zone' of every twelve hours before requiring to be cast on the subject again. Quite frankly I'm surprised that you managed to pull this off without being caught."
"Well, you do have to admit, as a couple and a royal couple about to get married at that, you're able to take certain liberties and excuses, such as being able to get more cake and being allowed to leave to spend some time together. I took the latter option to recast the spell, though I agree, the 'safe-zone' I have created for this spell is not at all practical and would wear down a normal unicorn in about a week of sustained casting, and most likely less for my changelings."
"Mhm, mhm..." Twilight continued to write down certain parts of the spell, skipping over some parts of it entirely, and adding new parts that Chrysalis would never have had thought of in the first place. The scritch scratch noise of the quill was all that was heard as Twilight continued to write out her version of the spell, with Chrysalis and Celestia watching her intently, both waiting to see what would be done.
Eventually, Twilight finished off the newly revised spell with a flourish, and smiled. "There! I have reduced magic consumption by fifty percent, increased the potency of the memory control spell, and done away with the safe zone! It is now a spell that takes instant effect upon the subject!"
Chrysalis was skeptical of this; after all, it was a very complicated spell, and as she browsed through the new spell system that Twilight had created for it, there was something off about it that Chrysalis couldn't place down. Unable to find it, she set down the parchment, and smiled. "Very good, Twilight! However, every spell is considered useless if it is not used. Come on, use it on me! We shall see what happens."
"Are you sure? I mean, I did just make it just now..."
"Twilight, you had my spell to base yours off on, and my spell didn't have too many negative downsides to it. Most likely all I'll get is a headache."
Twilight looked over to her mentor, who nodded slowly. "She's right, Twilight, there's not much that needed changing with the spell, so the idea of hurting Chrysalis is virtually slim."
"Well...Alright then." Twilight took one last look at her notes again, memorizing the spell system she created, and began gathering the magic needed to perform the spell. Sparks of magic flew from her horn and wrapped around Chrysalis' horn, orbiting it. It was about another five seconds before Twilight let go of the magic in her horn, and let fly with it.
With a loud bang, Chrysalis was thrown backward and propelled through a bookshelf, causing screaming from the other patrons of the library and panicked running from the rest. After exchanging a look with each other, Twilight and Celestia ran over to Chrysalis, who was on top of a pile of books with a dazed expression on her face. Fearfully, Twilight looked up at her mentor, who was gently prodding Chrysalis.
"I didn't think the spell would do that! I just don't know what went wrong, Celestia, I don't!"
"Well, perhaps it's because of the fact that Chrysalis is a changeling, and as such created this spell to be specifically used for changelings. You are a unicorn, so you must have tried to rewrite the spell with unicorn wiring in mind when this spell does not use them. I suppose that's why there was such an explosive backlash."
"That seems logical. I...Oh, she's waking up!"
Indeed, Chrysalis was waking up, with a snort and shaking her head around. "Ow...What happened, Tia, Twilight? Why am I on top of a pile on books, and why are there ponies screaming and running around?"
Celestia groaned, and began her explanation of what happened to Chrysalis, with Twilight offering little bits of information that Celestia didn't mention. When all was said, Chrysalis smiled, and got off the pile of books.
"Thankfully, I already don't remember this, Tia! That's one heck of a memory loss spell Twilight put on me!"