Twilight couldn’t help but feel frantic. If she couldn’t find some sort of counter to whatever it was Trixie had done to herself, then, well, she didn’t feel comfortable considering the worst case scenario. This whole situation was already a worst case scenario, she mused. She could faintly hear low rumbling noises in the distance, and tried very hard not to acknowledge that they were the sounds of Trixie getting bigger and bigger and bigger and bigger.

She gave herself a light smack, enough to shake her mind from that train of thought. As much as she didn’t really want to shake her mind from that train of thought, she was lucid enough to realize that the fact that she really wanted to return to Ponyville and get back to work was a very bad sign. The fact that she thought of pumping more and more magic into Trixie, making her bigger and stronger and more impossibly beautiful than she already was, as work was probably an even worse sign. Her face flushed as she turned back to the task at hand, thoughts of Trixie stubbornly lingering in the back of her mind as she surveyed her hideout.

The Everfree Castle wasn’t exactly the most comfortable place. Anything that wasn’t cold, hard stone had long since rotted away in the thousand years since it had been abandoned in favour of Canterlot. There were some sundry remains here and there - damp carpets, tattered tapestries, and of course the library. It had nothing on the Great Canterlot Library, but it would have to do. Canterlot was a day’s journey away by train, two on hoof - and she’d have to walk if she wanted to make it. Trixie could grow faster than that, and who knew how much bigger Trixie would get herself in that time? The last Twilight had seen of her, she had already started to dwarf the buildings of Ponyville.

In two days, she could very well dwarf all of Equestria.

And that would be just terrible.

Another light smack. Now wasn’t the time to get distracted. As reluctant as she was, allowing Trixie to get any bigger wasn’t an option. She squirmed. Right now she didn’t have much in the way of options. She could make the journey to Canterlot - the Great Canterlot Library almost certainly had the information she needed to put a stop to Trixie, or at least figure out what was going on - but Trixie could very well have conquered the world by the time she got there (which would be oh so terrible focus dammit). Perhaps Zecora knew something about what was going on, and could make some kind of alchemical shrinking potion. But if Twilight was susceptible to whatever mind control magic Trixie was using to encourage people to make her bigger, so was Zecora. For all she knew, Zecora was already brewing up a cauldron full of growth potion in the just crusade to please the Great and Divine Trixie no stop that.

Or she could hope that there was some information in the meagre library left in the Everfree Castle. She grabbed a moldering book off the shelf, Magic and It’s Effects written in faded lettering across its spine. “Well…” She scanned the shelves, praying to find something better without an obvious typo in the title, but none of the other books looked any better. Dictionaries, entomology textbooks, and pop-up childrens’ books. At the least the one she was holding now seemed vaguely related to her problem.

“If I have to,” she sighed, taking Magic and It’s Effects over to a desk. A few not-too-shabby pillows, a couple of the more useless books for support, and she’d managed to make her own comfortable study spot. She opened up the curtains on a nearby window, hoping to get some extra reading light, and immediately realized her mistake. The window looked out in the direction of Ponyville, and the increasingly enormous mare dominating its horizon. She bit her lip, briefly transfixed by her view of the beyond-massive Trixie, now stroking a dark blue shaft the size of Ponyville’s clock tower. Tiny pinpricks of light struck Trixie’s chest as unicorns poured their magic into her, swarms of pegasi buzzing eagerly around her hill-sized tits.

“I should close that window,” Twilight muttered, struggling to tear her gaze away from the spectacle. A hand ran down beneath her skirt, teasing her swollen pussy through her soaked-through panties. She sighed. “I should… Should really... “ No. She shook her head, finally looking away. The window had to stay open. She needed the light, and it would be good to keep an eye - or maybe both of them - on her enemy’s progress. At some point, she simply had to trust in her own self-control.

Hopefully that wasn’t her libido talking. She sat down, wiggled herself into the cushions to get comfy, and began reading. Eyes, trained for years to drink in text and soak up knowledge, scanned over the pages. This was it. This was her element. If she couldn’t beat Trixie by slinging spells, she could certainly do it by studying. The first chapter was useless, a beginning tutorial on spells to clean bathtubs. The second chapter was much better, discussing magic sponges that drank in magic and grew in proportion to their intake. Aha! She grinned, eagerly flipping pages. This sounded promising.

“Oh yes, mmm, more…” A blush spread across her face as Trixie’s moans rumbled through the castle. Her eyes wandered briefly up from the page, daring another glance at the goddess through the window before snapping back to the text. She was so big now that there was really no escaping her. If you couldn’t see Trixie – yet – you would certainly hear her, the quakes of her arousal rippling outward across Equestria. And it wouldn’t be long before Trixie herself followed. Twilight shuddered as she imagined Trixie growing big enough to reach the castle in a single step, her over-ripe sack dwarfing the whole structure, cum streaming in thick rivers down her shaft and leaking through the roof. It wouldn’t matter where she ran to escape Trixie then. A single pre-orgasmic spurt would be more than enough to flood the whole castle. Eventually, and sooner rather than later, Trixie’d be too big to ever dream of stopping.

Which, she thought as she slapped herself again, was why she had to hurry. Her hand hovered over her damp panties, quivering slightly as she read the chapter in more detail.

“What,” she read aloud in an attempt to drown out Trixie’s distant moaning, “exactly, is a magic sponge? Despite the name, it has nothing to do with cleaning! At least not directly. A magical sponge is an object that, for whatever reason, absorbs ambient magic. Typically, the object will increase in size as magic is absorbed.” Nothing directly relevant, but Twilight wasn’t going to let that deter her. She began to skim, and skim, and skim, and nothing came up. Dejected, Twilight flipped back to the beginning of the book, hoping to find something useful in the table of contents.

“Chapter one, Introduction to Bathroom Magic, no. Chapter two, Magic Sponges and Their Many Uses, no. Chapter three, Basic Spelling, probably useless. Chapter four, How to Defuse Any Magical Bomb, no. Chapter five, Advanced Bathroom Magic, no. Chapter six, A Presentation of Prestidigitation, no. Chapter seven, Bullshit Fetishy Artefacts?” It couldn’t be that easy, could it? She flipped through the pages, stopping when she reached chapter seven.

And there, right on the first page, was the necklace Trixie had been wearing. “The Alicorn Amulet is a powerful sexual artefact that can have many effects, all of them titillating.” Ugh. It read like something out of a really poorly scripted porno. Twilight frowned and kept reading, trying to ignore the fact that Trixie’s moans were getting louder. More intense. Her breathing quickened as each moan made the air around her vibrate. The air around her was heating up – from either her own arousal… or Trixie’s. Either way, she was running out of time.

“Okay, so the Alicorn Amulet. Powerful magical conduit, deeply ingrained in the fabric of reality… Was originally designed to help its creator cheat in a magical duel! Yes, there we go! Useful information, finally!” Twilight grinned, her hand drifting back to her crotch. Everything was clicking into place. The Amulet magically enforced the rules of a magical duel. More specifically, it enforced the specific letter of the rules, as laid out before the duel officially began. The original creator of the amulet had worded the terms of the duel creatively to give himself an advantage, but that didn’t feel like Trixie’s plan, especially going over what she remembered of the terms of the duel.

“I’m allowed to use whatever means I deem necessary,” Twilight repeated, recalling Trixie’s words, “but she’s limited to normal spells and whatever… magical power… she can muster.” Her eyes snapped open. Of course! Trixie had not only exploited the Amulet’s power to enforce the rules, she was also twisting its rule-enforcing powers to use it as an exceptionally strong magical conduit. Channeling, directing, and amplifying all magic used in the Duel straight into her own body! No wonder! The more magic she, or anyone acting on her behalf, used, the more Trixie would grow, taking that magic to use as her own! And, presumably, that also extended to the mental effects Trixie had on other ponies. And, now that Twilight knew how Trixie was doing it, she could stop it.

Twilight closed her eyes and lit her horn for a few moments, before she felt a weight lifting off of her shoulders, taking her unnatural urge to worship Trixie, to feed her magic, to make her bigger – all of it was gone, leaving only the lingering arousal. “That’s the mind control dealt with, at least. Doesn’t stop Trixie, but at least I can think clearly now.” Well, more clearly – Twilight was still very, very horny, but now she could satisfy that with a quickie instead of feeding Trixie even more magic.

Hopefully her arousal hadn’t caused her to miss anything obvious, but already she was starting to piece together Trixie’s plan. More magic, more growth, more worship. Infinitely, for as long as the Magic Duel went on. If Twilight never lost, Trixie could always just appoint substitutes to feed her instead, tapping new sources of magic to boost her to ever greater heights. And because of the wording of the rules, anyone could be her substitute. Not just her friends, not just the whole town of Ponville, but any and every pony in Equestria. Including the princesses.

She shivered. If this Duel went on much longer, there was a very good chance that Trixie would become a genuine goddess. “But how do I stop her?” She buried her head in her hands. Knowing all of this was fine and good, but none of it presented a solution. There wasn’t a source of magical power in the world that wouldn’t just make Trixie bigger. Even if she surrendered – always a possibility, she supposed – Equestria would still be facing a pony nearly as large as a mountain.

“Ooh…” A colossal moan shook the castle. Scratch that. Equestria would be facing a Trixie exactly as large as a mountain.

And yet, that would still be better than an infinitely powerful Trixie, swollen with all the magic in Equestria put together. If she could put a stop to it all, or even just delay Trixie slightly, by giving up her own magic… wasn’t it her duty to do that? There was no choice, really. The rules of the duel were too restrictive, too simple. Even if she could somehow face Trixie fairly now, without powering her up, it wouldn’t matter. Trixie’s most basic spells were still several orders of magnitude more powerful than anything she could muster. Truly, it was hopeless. There was no weapon she could use, no secret spell strong enough, not even a loophole in the rules that would allow her to–

Wait. She mentally ran over Trixie’s wordings again, recalling exactly the rules set for the Duel. Rules that would be enforced, to the letter, by the Alicorn Amulet. A grin spread slowly over her face. “Yes,” she whispered, looking out the window and gazing at the massive blue unicorn beyond. “I think that would work.”

“Hm. I wonder if I could give a little bit of my magic to somepony else,” she mused. “I mean, it’s mine. I won it, I can do what I want with it, right?” She focused on the pink dot, smiling as new fantasies began to take shape. “And being a goddess on my own would get lonely after a while. I’m sure there’ll be enough space for five more...”