If the first part of the chaotic battle with Twilight in an unreleased state was her in an evasive mood, and the second was her in a teaching mood, the third and current part was Twilight in an agressive mood.
And Pinkie finally understood completely the reason why Twilight had told her to remain "at the edges". The chaotic unicorn followed up on her "throwing tree" gambit with turning the entire battlefield into an abyss of darkness that started to suck up everything around it. That strategy managed to actually force Discord to pay attention to her, but the earth pony had to repeatedly chaotic teleport on top of clouds to avoid being sucked up herself.
It seemed that the Knight had completely forgotten the notion of "fire control".
And that set the tone for the next few minutes of combat. Discord made the abyss spit back out everything it had sucked and threw it at Twilight, only for the unicorn to turn all that matter into a coordinated strike team composed of a weird hybrid of rhynoceros and elephants, who spat out multitudes of sharp horns from their trunks, blanketing the area on deadly projectiles. Pinkie had to party cannon herself onto one of the rhynophants and tame it to escape danger, and kept using her new mount, as she knew things would get even crazier from there.
And in fact they did, the spirit of chaos responded to that attack by turning all the projectiles around into wind-up toys capable of firing laser beams, which he set upon Twilight's own troops.
And things kept escalating from there, with Twilight's wave of sharp teeth, rain of lightning fish and a hydra made of portals clashed against Discord's mountain of hands, volcano of iron dentures and winged fish wielding a dimension cutting sword. Through all that, Pinkie had no chance of actually getting involved, and simply did her best to try and avoid injury.
But Pinkie Pie still had enough awareness remaining to see something that seemed particularly out of place, even in that kind of weird battle. It was when Twilight created dozens of copies of herself, each one with a different color scheme, and set all of them to attack Discord. One of them (with a grey mane) disobeyed that order, and floated off to observe the battle from a certain distance, but neither Twilight nor Discord seemed to have even noticed that something was wrong. And that copy seemed to be immaterial and completely impossible to affect, since all kinds of attacks and types of energy passed through her without having any effect.
And there was a lot of those. Twilight's self duplication gambit had managed to achieve something which had seemed impossible previously, and actually put the spirit of chaos on the backstep.
Twilight seemed to have completely given up on well-realized attacks and was simply using pure chaos magic shot by each and every one of the copies. Instead of reaching their target and activating like normal spells, Twilight's blasts of magic distorted the world around them even as they travelled through the air, causing random transformations, bending space and even releasing blasts of magic with their own effects all around.
This seemed to be too much for Discord, specially due to the fact that the unicorn's focus was entirely on him, to the point that Pinkie could actually breathe easy (though the sheer amount of offensive chaotic power in the air was making her sick in a methaphysical sense[which was as weird as expected]). But then the party pony looked at her teacher and saw something worrying.
Her form seemed to be wavering slightly like a mirage. Pinkie rubbed her eyes to try to clear them, but it kept getting more obvious. And then her colors started getting dangerously vibrant and shiny. And then her body started vibrating.
And yet, Twilight kept laughing while she and her copies launched attacks, seemingly completely oblivious to this change.
Pinkie Pie felt, through her Pinkie Sense, that something very bad was happening, but she was incapable of sensing what exactly it was. She was thinking about interfering with what was happening in some way...
And that was when the gray Twilight acted.
Putting her fron hooves forward, she flew incredibly quickly to Twilight's main body and fused with it. Twilight suddenly stopped laughing and moving, and the same happened with her copies. Then every single copy was sucked towards Twilight and fused with her, along with every single spell they still had in effect, creating a huge maelstron of chaos that spun around the unicorn and was sucked up.
Finally, Twilight's body returned to normal, she stopped wavering and vibrating, and her colors went back to normal. Then she fell to the ground, groaning.
Pinkie didn't even think about it, she shifted to Twilight's position and tried to see what was wrong, but there didn't seem to be any injuries in the unicorn's body, and her Pinkie Sense was telling her that Twilight wasn't at risk.
"So, you've finally hit your limit on the Chaotic Release." Discord said in a victorious tone "It was very strong, and it is rare for anypony to return to normal instead of exploding when the technique ends... But you've still lost."
Pinkie Pie looked at him fiercely, she was preparing her mind to fight Discord one-on-one.
Yet, he seemed unperturbed.
"With this, I will take my prize. Both of you will be my apprentices from now on." He pointed two fingers at the ponies, and did something completely unexpected.
He started charging magic.
It took only a second, but it was still more than he had ever done in the fight. And from that, he shot two arrows made of black light at the ponies.
When Pinkie Pie saw the arrows, her Pinkie Sense practically screamed "RUN AWAY!" at her. So, the party pony held Twilight and chaotically jumped as far as she could. Despite carrying another pony and being already tired, her distance reached thousands of meters.
But it didn't matter.
The arrows seemed to shift, and they simply moved the same amount as she had. And they were moving fast, too fast.
The earth pony didn't have any option except try to shield Twilight with her body, even knowing it would do no good.
"Magic Enhance: Grand Arrow Shot!" Sunset shouted, using her fastest spell, creating a powerful arrow of light that contained all of her will to take down Discord's magic. It was a phenomenal feat of magic.
But it just wasn't fast enough.
Trixie, Applejack and Rarity appeared near the battlefield. The unicorn Knight immediately started charging magic. She saw from his comments that Discord was trying to control the two ponies, so she started thinking of spells to break that control.
Rainbow Dash dove.
She cursed her own lack of luck. Pinkie's teleportation had put her too far away from the pegasus. Even with maximum speed, she simply wouldn't be able to reach the ponies in time.
The entire world seemed to slow down as she accelerated, until Rainbow Dash touched a very familiar barrier, which stopped her from going faster.
But she still wasn't fast enough to reach Twilight and Pinkie. So she ignored the pain in her body as she pushed her magic harder than she ever remembered doing. Her teacher had put her in charge of saving the two if necessary. Rainbow Dash wouldn't disappoint Sunset, Rainbow Dash wouldn't break her promise, Rainbow Dash wouldn't let those two heroes be hit.
The pegasus willed her body to move, and in that moment, she forgot everything and the only thing left in her mind was reaching her goal.
And faced with such an extraordinary will, the barrier broke, and suddenly Rainbow Dash accelerated beyond anything she had ever felt, overtook the arrows, grabbed the two ponies and flew into the sky, seeking safety.
Neither Rainbow Dash nor her passengers were in a position to see the effects of the pegasus' movement, but Sunset, Fluttershy, Applejack, Trixie and Rarity were. They saw a beautiful explosion of planar rainbow energy, and each one of them had different thoughts about it.
Fluttershy was nostalgic, remembering the first time her friend had done it. Sunset was proud of her student finally managing to surpass her "wall". Trixie was thinking of how amazing it would be in a show. Applejack could see the sheer purity that Rainbow had when she managed it, and thought this was something she would never forget. Rarity thought that Rainbow's last-second rescue and the explosion were magnificent.
But those thoughts were soon replaced when the edge of the expanding rainbow circle reached the spirit of chaos.
His scream was horrifying and chilled the blood of all who heard it. And when they could see the result of the sonic rainboon having passed through him, they were completely shocked.
Discord's body had become distorted, with each distinct part seeming to have grown of shrunk in proportions, and there were deep cracks running through the whole thing, leaking some sort of fluorescent and multicolored liquid.
The spirit of chaos started breathing heavily and seemed to struggle to move his own hands, but when he got in position to do another spell, a beam of light suddenly struck him.
He turned in shock as the light disappeared and bands of light appeared on his arms and legs. Then his face became angry and he seemed to blow up, creating a short-lived cloud of dust that cleared to show that his proportions were back to normal. But the cracks in his body were still there, same with the bands of light.
Sunset, Trixie and Twilight(who, along with Rainbow Dash and Pinkie, had heard Discord's scream and looked in his direction) immediately realized what was going on. Princess Celestia had taken the opportunity to hit Discord with a spell to seal his chaotic movement, preventing him from running away after being weakened by the attack.
But Discord wouldn't make that easy. Seeing that this was a fairly unoptimal situation, he did the best thing he could and ran into the Everfree Forest, ignoring the rain of spells Sunset was unleashing on him, before waving his hand and causing every tree in the forest to grow and create a barrier to prevent others from following him.
Rainbow Dash landed next to Sunset, letting her passengers off, and Trixie and her students also moved there. The three Knights knew that time was of the essence, so they had a conversation via looks:
(Sunset: You saw that right, Trixie? Can you reproduce it?
Trixie: Yes, I can. Think we can do a World Create?
Twilight: We can, but we'll need to Overdrive too much to get enough power, even weakened like he is, Discord will not go down to a half-hearted attack.
Trixie: Then I'll need your help to create the spell formula. I forced myself too much on my mission, and making a complex enough illusion would already be difficult even if I was 100%.
Sunset: That's okay, but we need a way of getting Discord before he can reach the source of chaos magic in the middle of the forest and recover.
Twilight: I and my apprentices will deal with that.)
"Fluttershy." Twilight looked at the pegasus seriously "Discord has made the forest reject us so he can get to the center unopposed and recover." She watched as the animal caretaker took on a look of defiance upon hearing that "I'll need you to talk to the entire forest and get it to accept us, so that me and Pinkie can move us in and intercept him."
Fluttershy seemed hesitant for a moment before nodding "I'll do my best."
Sunset teleported them close to the forest and Fluttershy approached one of the trees and touched it before closing her eyes and focusing. It took only a few seconds for all the ponies around to start feeling the amount of magic Fluttershy was using to try and complete her mission. Sunset actually opened her mouth to say something about it but Twilight silenced her with a look (not a communication look, just a normal one).
Her faith in her apprentice proved to not be misplaced. Fluttershy's body started to shine brightly and then the trees returned to normal, opening a passage for them. Fluttershy started breathing heavily from the effort, but was still okay.
"Fluttershy only loses to you among all the ponies here in terms of magical power." Twilight explained quickly, before nodding to Pinkie Pie. Both of them focused and took a step, moving through the forest at chaotic speed and carrying the rest of the ponies with them.
They reappeared in a rather deep part of the forest, next to a river in a position that would allow them to easily spot Discord as soon as he made his way through the trees.
Wasting no time, the three Knights adopted a triangle formation and started casting, slowly creating a ridiculously complex structure that Rarity only faintly recognized as a spell formula.
But Discord turned out to be faster than expected, and he got there before the three were ready to unleash their magic, if barely.
But at this point, Fluttershy's emotions overflowed. She had been seeing all the bad things Discord did, all the homes that were distorted, all the ponies that had been turned into monsters... She thought of all of that, and in the moment where Discord was surprised to see the ponies he thought he had outrun before him... The pegasus Stared at the spirit of chaos.
It could only be described as the eyes of ten thousand disappointed mothers concentrated on a single point, and Discord was frozen to his spot out of pure conceptual shame. and it worked for three entire seconds, practically an eternity under the circunstances. Specially because the Knights were ready after two.
"OVERDRIVE!" All three shouted, releasing an immense amount of magic from their bodies, more than they had ever used with that technique, enough that their combined magical power started to distort space around them.
But it was put to use quickly.
"Everything that exists can be faked...
"Perfect Illusion: Harmony World!" Trixie shouted, and the magical formula created by the Knights lit up as she channeled her magic through it, allowing for the impossible to occur via Trixie's own will and abilities.
And the effect was colossal, for an entire world appeared around Discord. It was a small world but it possessed everything a world needs to exist, its own laws, a diferentiation between spaces, as well as a firm structure. Creating even such a small world was supposed to be impossible for ponies, but it was only an illusion, so Trixie could barely do it.
And the law of the world was harmony.
If Discord could have, he would have grimaced at such a thing appearing around him, but it was only an illusion of harmony, instead of the pure stuff, so it wasn't harmful for him.
But the Knights were not done yet.
"With trust, nothing is impossible...
"Soul Offering!" Sunset shouted, using one of the spells she was most proud off. Having so much magic power, the yellow unicorn had hit upon the idea of sharing some with her partners so that they could perform spells beyond their regular capacity. That was the first time she had actually used it in battle, and Sunset was surprised over the fact that even that first use had to be done in combination with an Overdrive.
And it wasn't just power. As Twilight received the technique, she could feel a veritable connection between Sunset and herself, as the Soul Offering was not an hyperbole, and the powerful Knight had put her own essence under the mercy of the chaotic unicorn.
This was the main reason why this spell was so powerful.
"The boundaries of the world move under my will...
"Boundary Sign: Reverse Boundary!" And it was a sign of how monumental was the spell Twilight was attempting, that even with Sunset's Overdrive in addition to her own, an amount of magic power that could be described as obscene, Twilight still barely managed to cast the spell.
But she did manage, and the effect was worth the cost, for in the area occupied by Trixie's illusion, an entire concept shifted, and the boundary between reality and illusion... flipped.
Turning an illusion of a world of harmony into the real thing.
"COMBINATION ATTACK: WORLD CREATE!" The trio of Knights shouted.
The world lasted for only a moment before Trixie's power was unable to keep such a thing in the world, but it was more than enough.
Discord didn't even have time to scream, as his form exploded into thousands of pieces of chaos magic, that flew off in all directions, causing a commotion to all that were looking at the sky.
But neither the Knights nor their apprentices had any time to think about it, because the effect of the Overdrive hit and the three fainted.