"Pinkie, use the slipstream!" Twilight alerted her apprentice, that being the only instructions she could possibly give for the duel, considering exactly what kind of duel it was.
Discord opened with creating a monster that seemed to consist entirely of mouth and setting it upon Twilight, but before the unicorn could do anything against it, Pinkie proved that she had listened.
"YEEEEHAAA!" Suddenly, she was riding in one of the monster's teeth, somehow avoiding being cut by its extreme sharpness and controlling the beast despite it having no nerves or anything else that could potentially be exploited by a rider to control a living ride. She turned the mouth back against Discord, who turned it into glass and shattered with a summoned hammer, creating an entire shower of glass shards flying towards the ponies.
Twilight was the one to deal with that attack, turning the glass shards into bouncing balls, that bounced off the ground and shot back towards Discord at a much greater speed. She was also using slipstream.
The slipstream was the name the unicorn gave to one of the discoveries she made about chaos magic. Said simply, it took less energy to affect something with chaos magic if it "followed" the use of a higher amount of that same amount of magic. It was actually fairly complicated and confusing, but that was the gist of it. And Discord was using a lot of chaos magic, more than enough for them to be able to fight without using that much magic.
That was important, because while the two could do all those things by themselves, they would rather not wear themselves out by using too much magic too early, since this was a fight where the main goal was to last as long as possible.
So the fight continued in the same vein for a few more exchanges, and the preferences of the three involved in the battle gradually became clear. Discord, with his immense age and power, was attracted to big and flamboyant displays, as well as making references to things only he would understand. His spells were full of strange mechanisms, weird languages, ancient beasts, and tended toward the big and loud end of the spectrum. Twilight on the other hand, was an expert in mystery and orderliness, reversing spells in unexpected ways as well as making order itself the punchline used by her magic, like when she made a swarm of bees do a synchronized dance routine. Traces of the influence of her partners could be seen in her manipulation of position for unexpected attacks and in her quick escalation of small spells. The fact that she also started reciting a speech about "the true nature of chaos magic" and everything she had gone through to learn it also helped. Finally, there was Pinkie Pie, who didn't have nearly as much power to spare as either of the two, so focused on creating the greatest effect by changing the least possible. However, it could easily be seen that the root of her chaos magic tended towards fun, with all the party themed effects and her trying to make friends with a lot of the spells Discord used.
Still, a fight between specialists in chaos magic would never be able to remain static for long, and it was Discord who decided to change the script. By turning a statue Twilight was making spin into himself, he got close enough to touch her horn. The unicorn quickly gathered all the power she could to repel him, but on such short notice her hasty defences couldn't help but buckle under his overwhelming power. And her horn disappeared.
"Oh, how sad... What will the little unicorn do without her horn?" The spirit of chaos asked mockingly.
Twilight Sparkle glared at him, then she extended her hoof to Pinkie, who took a party hat out of her mane and gave it to her.
Twilight stuck the party hat in her head, and it glowed, gathering magic.
Discord was unable to react before Twilight blasted him with a spell that split him into the several animals his body parts belonged to. He quickly reformed himself, only to be hit with one of Pinkie's party cannons, getting the battle going again.
Fifteen Minutes Earlier...
The six other ponies, who had left the area to allow the fight to proceed unhindered, got to a safe distance before stopping.
"There's no time for politeness, so I'll be quick." Sunset said, with a serious face "Me and Trixie have received our mission. Do you want to help?"
"Of course!" Rainbow Dash didn't even hesitate.
"I agree." Rarity was only a little behind "I may not be a Knight, but I will do what I can."
Applejack and Fluttershy (the pegasus with an uncharacteristic fierceness) also agreed to do what they could. Sunset nodded.
"Right then. Trixie, how are the princesses?" She asked.
Trixie cancelled the spell she had been using "Seems like Discord trapped them in Canterlot."
Sunset considered that "Then we have two objectives to try to accomplish while Twilight and Pinkie are giving us time. We need to rescue the princesses, so that they can give support, and we need to fix as much of the chaotic effects as possible around Ponyville, since less chaos nearby will weaken Discord." She then looked at her partner "Trixie, you should take your apprentices and go to Canterlot, since you can probably use your illusions to conceal when the princesses are released. Do you have any better ideas?"
Trixie shook her head "No. This seems like the best use of Trixie's talents." She turned to her apprentices "Applejack, you should try to use your Eyes of Truth to find the centers of magical activity, since those are the places the princesses will be trapped in. Rarity, Trixie'll show you a spell based around returning things to a 'whole' state that will serve to deal with smaller chaos effects. But!" She said suddenly "If you think of other ways to help, don't hesitate."
Applejack and Rarity nodded at this.
"Right. So Rarity, keep an eye on this spell formula..." Trixie started casting a spell while deliberatedly writing the formula visibly and slowly.
Meanwhile, Sunset had turned to the other two "Fluttershy, you should be able to use your empathy to find distressed ponies, which will definitely be near the biggest sources of chaos around. Take me to them, and give whatever support is necessary. Rainbow Dash, you will have the most important job." She looked at the blue pegasus with an extremely serious expression "Keep a safe distance from the fight and be ready to rescue the two of them if they get in trouble."
Rainbow Dash replied "I understand." With a completely serious expression and went flying to do her job.
Fluttershy closed her eyes and focused for a few moments before pointing out a direction, then the two set off.
After Trixie finished demonstrating the spell, Rarity tried and failed to reproduce it, but a bit of additional instruction by the blue unicorn allowed her to suceed on the second try.
"Then, let's go." Trixie said, and charged up a lot more than usual, because teleporting three ponies took a lot of energy.
And with a sound that was much less elegant than Trixie's usual teleports, the three ponies disappeared.
Twilight had the opinion that things could be going a lot worse.
Her thoughts were because of her apprentice, Pinkie Pie, who turned out to have the right abilities, mindset and level of skill to remain standing in a fight against the Spirit of Chaos, Discord.
At the beginning of the battle, Twilight kept a lot of her attention on the pink mare, ready to help the party pony in case it was necessary. But over the course of their duel with the draconequus, she started to relax her vigilance more and more, as Pinkie kept getting out of dangerous situations under her own power. Her abilities were entirely suited for the task, as she had a lot more ease in manipulating her own body in chaotic effects than Twilight herself. Pinkie could split herself in two to evade a cut, flatten herself in response to being crushed, easily reversing the process, or simply disregard injuries by turning them into jokes, acting like she was an actor who was only pretending to be hurt. Not to mention her skill with the chaotic movements and the fact that her Pinkie Sense could predict Discord's most dangerous attacks.
As for her mentality, the simple fact that Pinkie Pie was keeping her cool even though this was only the second time she had been in a dangerous situation was already enough to estabilish her will as firm. Pinkie seemed to be able to maintain a belief that things would be alright, and was more than ready to make an effort so that would come to pass. Most ponies would be overwhelmed by the pressure of the situation, lose sight of their objectives or simply lose focus. But Pinkie had spendidly avoided all those pitfalls and was doing impressively.
Finally, there was the question of Pinkie's skill. Because even with the right mindset and abilities, it would still be useless if she could not apply everything correctly. And the earth pony proved to be a prodigy, managing to use the right abilities at the right moments, advancing and retreating based on the situation of the fight and even observing Discord himself to figure out when the flow of the duel would change. She was clearly growing during the fight, being able to react a lot faster than the beginning, and she even started doing her own (sort off) speech, about how she was going to throw Discord the best party he had ever seen.
But still, there were limits to everything, and the draconequus finally managed to find Pinkie's.
She had just managed to make him choke with a confetti bomb, and Discord actually created a portable spatial distortion in between his hands to retaliate. Twilight gasped when she saw that, and immediately activated both of her prepared spells to execute the mix:
"Merged Spell!" She shouted, willing her magic to go fast enough.
While she was doing this, Discord had managed to enlarge his spatial distortion to the point it became a house-sized sphere of whirling chaotic energy and threw it at Pinkie.
The party pony tried to use her chaotic movement to dodge, but that technique was, at its heart, a manipulation of space, and the very nature of Discord's attack caused enough disturbance in space that she couldn't find a path to move through, despite her unusual skill at the technique.
And the distortion swallowed her up.
She wasn't hurt by it, but the effect of Discord's attack could be compared with the spell Twilight had used against Sombra during that battle, Sidestep. But a comparison was all that could be made, because Discord's spell was on a completely different level. It created a cage of space around the pink pony, isolating her conceptually from every connection with the world, with a brute force approach that simply left no room for any clever tricks.
But Discord wasn't the only one who could use brute force.
"Freedom is the wish of all things...
"Open Sign: Release Magic!"
If Discord's spell had been conceptual isolation, Twilight's counterspell was conceptual acceptance, drawing all of existence (locally) into itself and rejecting nothing. This time, it was Discord's magic that buckled under the strength of an opponent's spell, partially due to the power of the merged magic and partially due to the conceptual advantage. The cage of space that had already left the world was forcefully brought back into reality and dissolved into its component parts, which were absorbed and used as additional energy for the spell to deal with the parts of the magic that weren't physical.
Pinkie was dumped on the ground, dizzy.
"Should make a party for escaping from that nasty spell..." She said groggily, before shaking her head and refocusing.
Twilight sighed in relief and got back to the fight. But inwardly, she was very concerned about how things would go from then on. She had no more prepared spells, and while Discord probably wouldn't use such a powerful and dangerous attack again all that soon (it would be too much like repeating a joke), having lost that trump card meant the unicorn had much less room for maneuver.
She hoped thing were going better for the others.
Despite the danger of the situation, Sunset could not help but have fun.
"Magic Enhance: Explosion Chain!" She cast, creating a series of explosions that destroyed a huge golem that had been preparing to swing a fist at her.
And why should she not be? While her partners would probably try to be elegant and disable the chaos effects with complex spells, Sunset preferred to simply smash them with pure power. Not that it was completely mindless, because it was only Sunset's experience in handling chaos effects that allowed her to target her magic effectively, but it was very far from being complicated enough to impair the unicorn's enjoyment of the situation.
Even the fact that she had to keep Fluttershy safe while she was fighting only played into the scenario, as protecting somepony who was precious to her partner while she was away was a common ocurrence in the old tales.
After the destruction was complete, Fluttershy flew into the remains of the golem, pulling out a green foal.
"Are you okay? Don't worry, everything is going to be alright." The pegasus conforted the crying foal for a bit, then put him on his hooves "You need to leave this place, go back through there and you will be able to escape." She pointed out a direction and the foal thanked her and went.
Then, Fluttershy closed her eyes and concentrated before pointing in a new direction "This way!" She took to the air, but fhew slowly enough for Sunset to overtake her with her magic enhancement.
They still had a lot of work to do.
Meanwhile, Trixie's group was going through the streets of Canterlot.
Not that they could be recognized as such just from seeing them. When they got there, Rarity had expressed annoyance with the fact that her first visit to Canterlot happened when the city was twisted in that manner. Buildings had distorted proportions and weird structural gaps, the rivers were flowing through the air, and twisted into crazy routes that made them look like rollercoasters, the trees had started walking around and taking pieces of the buildings to eat, and even the ground had distorted to the point that all kinds of sharp cliffs, spiralling depressions and other geographical oddities were popping up, making getting from point A to point B an arduous task.
The group of Knight and apprentices had completely different tactics from Sunset's duo. This was because their goal wasn't to remove every source of chaos they could find, but was instead to reach the princesses and free them. The three ponies tried to avoid as much as they could of the chaotic creatures that were running around the place, with Applejack using her Eyes to see the best paths to get closer to the castle, Trixie using her illusions to distract the creatures and lure them away, and Rarity using her telekinesis to help the group move through the difficult terrain. Besides that, Applejack kept trying to see further away to locate the exact position of the princesses (she had already realized that they were in the direction of the castle), Rarity was using the spell Trixie taught her to deal with the monsters that got too close and Trixie was using remote vision spells to monitorate both the space around them to avoid possible ambushes and the fight between Discord and the pony chaos wielders.
As expected, Trixie had the hardest job. Even just keeping watch of the surroundings would already be the hardest job, due to the amount of focus it took to keep the stability of the spells and make sense of the distorted space, but Trixie was also looking at Discord, so that she would know if the situation changed and they had to quickly change their plans. Trixie was continually thinking of all the possibilities of things that could happen, and their responses to them.
"Ah got it." Applejack suddenly spoke up "Both princesses are in the same place, one of them towers in the back of the castle, in one of the lower floors."
Trixie nodded "Good work, let's go there. But there's a place we need to stop by in the way."
"Why do we need to stop somewhere?" Rarity asked.
"To create an illusion big enough to cover the entire city, Trixie will need access to the magic formation." Upon seeing their blank looks, Trixie explained "The magic formation is a special place where the Knights can harness the power of the city itself. It was created so that Canterlot could be defended from powerful threats."
The two apprentices nodded in understanding, and they went back to the task of moving through the city, it didn't take long for them to get to the place where the magic formation was put.
"Trixie..." Rarity asked slowly "Was there something about chaotic creatures being attracted to big concentrations of magic?"
She said that because, on the circle that delineated the space of the formation, countless monsters were gathered, creatures of all kinds of shapes and sizes, all of them seeming completely unwilling to leave.
"Trixie seems to recall something like that from her studies, yes." The blue unicorn answered in a blank tone.
"Ah guess things could not really be that easy, right?" Applejack said what they were all thinking.
Twilight was currently facing a difficult decision.
She was already beginning to feel tired from the continuous effort of the fight. She could still keep going for a while, but her focus and reaction speed would start dropping. And from what she could see, Pinkie Pie was only slightly better. Worse still, from the flow of the battle and Discord's movements and expressions, she could guess that he would use another powerful attack very soon, and she couldn't be sure of being able to deal with what he would do, considering his abilities were very unpredictable.
She would then have to Overdrive, leaving Pinkie facing Discord alone for far too long.
No, she had to do something else instead, even if it was very reckless, she couldn't simply leave Pinkie in danger. So she opened her mouth and called her apprentice:
"Pinkie! Grab two of the red potions!"
Pinkie saluted and warped to the library. It was good that she had already shown her apprentices where she kept the spare potions, just for fun. Twilight kept Discord's attention on her by using a sequence of three spells that were an entire level stronger than what she had been using before, since trying to preserve her strength didn't matter as much anymore.
The earth pony reappeared very quickly, carrying the two bottles, Twilight grabbed one of them with telekinesis and spoke:
"Drink the other one."
Both ponies quickly drank the red liquid and felt their muscles relax. This should give them enough endurance to keep fighting at a high level for while still, but this would not be enough to deal with Discord. So Twilight spoke a few more words to her apprentice:
"Stay on the edges, I'm going to release all my restraints."
Pinkie looked at her in shock, then nodded at Twilight's expression and moved away. The unicorn closed her eyes, and a few meters away, Discord stopped what he was doing (turning a gust of wind into a fish) upon sensing something coming from her. Twilight went to the depths of her mind and looked at the representation of her determination and self control, heavy golden chains that seemed to contain an entire identity, and were holding a small kaleidoscope of chaotic colors. The unicorn focused on the kaleidoscope and it grew, utterly shattering the chains, and kept growing and growing to the point it swallowed up Twilight's consciousness, and nearly every bit of space on her mind.
Outside, Twilight's shadow seemed to shift, and then it smiled. Twilight herself brought her hoof to her mouth and giggled.
"Hi, hi, hi..."