The Knights did what they could. Sunset and Pinkie Pie used the immense amount of power they had access to in a very rough manner, liberally throwing energy at the approaching flames to try and at least slow them down. Rarity spread the water she was controlling to all of the Knights, trying to create heat sinks to prevent them from burning even before being hit.
Neither of those actions would be able to do more than slightly delay the death of the Knights, but thankfully, Rainbow Dash did her job.
With a wave of a hoof, extremely powerful winds were created by the pegasus, who then flapped her wings, connecting the winds to her own control zone and taking off at the amazing speeds she was famous for. The winds were dragged with her, and they swept up the other five Knights, forcing them away from the instant death zone. The movement was very rough and unrefined, but speed was of the essence, and while normal ponies would probably break quite a few bones in such a situation, the Knighs were hardier than that.
Still, even with Rainbow Dash's quick actions, the Knights were not out of danger. The spells that Flames was using have achieved a newfound level of power after her Trance mode, and even with Rarity having created a heat sink, the temperature of the flames was enough that the Knights were forced to flare their defensive auras recklessly just to keep from being cooked alive.
A second passed, and even that ceased to be enough as all the water boiled away into steam and they had to endure the heat by themselves. But then Sunset, still in her own Trance Mode, shot a series of quick barriers that blocked part of the energy of the destroying flames.
And Rainbow Dash accelerated, pulling them even harder to the point where they were finally out of danger. The Knights stopped flaring their auras and felt some pain from their muscles due to how hard they had channeled their magic in order to endure. Another second passed and they finally reached outside the range in which the flames were disturbing any teleportation, and the three unicorns joined their powers to teleport the group away and into their third interception position.
The six collapased on the ground in an undignified manner, the extreme effort they had gone through in such a short time combined with their previous exertions being too much to allow them to handle their state in a cool manner (as much as they wanted to).
Rainbow Dash, Sunset and even Pinkie Pie canceled their own special modes, since they needed to conserve their strength as much as possible. Wordlessly, Pinkie Pie grabbed another six potion bottles for them to drink, but that was pretty much the limit, the second dose was still effective, if noticeable less than the first, but any other doses of the potion would have only marginal effects.
The six rested for a bit and checked the condition of their own bodies, knowing that any small problem they missed could be fatal. But after that was done, came time to talk:
"Sunset... You said her Trance Mode wasn't stronger than yours..." Rainbow Dash spoke slowly "So what was that?"
Sunset shook her head "It isn't inherently more powerful, but she was using Forbidden Shift, which means she was deliberately ignoring the limits of her own body to get the most power possible. I could technically do that as well, but it's not worth it because your body starts to decay from the inside." She stopped for a moment "I guess she is using fleshmolding to keep regenerating herself, but I can't imagine the pain she must be feeling."
Pinkie sighed "Everything we learn about this pony makes her seem more and more messed up."
There was a general silence of agreement.
"Okay, now that we understand what's going on, what is out plan?" Rarity asked "How are we supposed to get through that?"
"It's going to be difficult." Trixie was the one to speak "With the way she is now, simply attracting her fire to other directions won't help much, because the simple side effects of her attacks can kill, and because she increased the power of her flames so much that even getting close to her to try and take advantage of a distraction could prove lethal due to the passive spread of her power. The magic of destruction becomes a very effective defense at this level."
"What are her weaknesses, then?" Sunset asked. Trixie looked at Applejack, who immediately understood what she was getting at.
"Most of it isn't really things that will help us a lot." She started "Even after using Trance mode, Ah could see that she is still under the restraint effect of the spell of the princesses. With that she should only be able ta use around eighty percent of her full power. There is also the fact that she is pushing herself far too much in terms of self healing. There is a limit ta how much ya can heal with magic, especially when it comes ta magic exhaustion. It was still under control before, but now that she is using that special Trance Mode, forcefully healing herself is pretty much the same as consuming life for power. Ah think that she won't be able ta survive until tomorrow, no matter what we do."
She sighed and went back to her observations:
"Of course, it won't matter ta her as long as she can kill the princesses, and Ah think this is something we can use. Creating illusions that look like the princesses, it's possible ta make her confused, but she definitely will be able ta tell after destroying them." She closed her eyes "Also, while her defense must have increased due ta the Trance Mode, it should not be ta the same degree as her attack power, because it's harder ta turn pure power into defense than it is simple destruction, specially for somepony who lost most of herself in exchange for power... In fact, now that she needs to use extra power ta heal herself from her own power, that makes it easier for some kinds of attacks ta be able ta injure her."
"Hmm..." Trixie thought hard about it "Trixie believes there is no reason to use spell circles to enhance us in small ways like we were doing before, since there is no way it could be enough to matter against what we are fighting. Instead, Trixie proposes we use a single massive spell circle to take advantage of the efforts of the princesses."
Rarity was the first to get it "Ah, you mean similarity, don't you?"
The showmare nodded "Exactly. By creating a power sealing spell circle that can connect with the spell used by the princesses, we should be able to increase the level of sealing on her powers. It could be possible to reduce her to only 50-60 percent of her usual." She put a hoof on her chin "Normally, this would be difficult, because it is almost impossible to hide the resonance such a thing would have on the target, and they wouldn't simply walk into the target point, but Flames of Annihilation won't deviate from her route no matter what. The only problem is that the circle will have to be really big and spread out, otherwise the simple effect of her walking close would destroy it."
She stopped for a moment, before continuing to speak "And while it is difficult to affect her with internal illusions because of her passive magic resistance, Trixie believes that a special prepared spell should be able to exploit her obsession with the princesses and trick her into removing the defenses around her heart, but to actually deal with her..." She looked at Sunset meaningfully.
Sunset nodded gravely "I have an idea, but it will be dangerous." She looked at her apprentice "I am talking about plan C."
"Plan C?" Rainbow Dash was surprised "You mean... But that means..."
"Yes. We are going to have to endure one of the attacks of the Flames of Annihilation."
Upon performing her Soul Emulate, Fluttershy immediately gained a profound understanding of the abilities of her enemy, specially the "golden mist" that he created, and because of that, she got very motivated to avoid letting the stallion approach even close to the end of the room where Twilight was standing.
His ability could be roughly classified as part of the enchantment type. Essentially, the golden mist was just an ordinary mist that had been altered with magic to acquire incredibly deadly properties. This was a particularly versatile ability, because "Mist" (she had to call the enemy something, didn't she?) could not only manipulate the physical properties of the mist, like making it extremely resilient to use as a shield, but he could also manipulate the magic properties of it as well, being capable of such things as blocking and delivering mental attacks. And of course, that was only scratching the surface of what he could do.
But now Fluttershy had the exact same abilities as him. Her Soul Emulate wasn't truly perfect (yet), but copying the powers of a construct of a powerful warrior that wasn't as strong as the original (which she could feel with her empathic abilities) was something she definitely could do. Fluttershy was ready, and while Mist was surprised for seeing her using his ability, she advanced and attacked him first.
Forming her mist into a spear, Fluttershy tried to pierce through the mist of her opponent, but even surprised he wasn't helpless, and managed to deflect the spear away before it could pierce more than a few centimeters. Then he counter attacked, lashing out with a tendril that was enchanted with cold and managed to freeze the surface of Fluttershy's own golden mist before she enchanted heat and melted away the ice.
After that, she sent a dart of golden mist with a chaos enchantment flying to hit her enemy. It forcefully altered the attributes of the enemy mist and scattered it, allowing Fluttershy a chance to advance in a ramming attack to try and finish her enemy off quickly.
But of course it wouldn't be that easy.
Mist flapped his wings and flew backwards to get a bit of time to reestablish his mist. He managed it a moment before Fluttershy hit him, dragging him forwards as both their mists ended up entangled. He used that opportunity to enchant parts of his mist with piercing properties, sending five arrows of mist at his opponent at point blank range.
Knowing that blocking would be difficult, Fluttershy enchanted 'stop', forcefully making her own mist 'grab' the arrows, turning them to her control.
And so their fight proceeded. While Fluttershy had exactly the same abilities as mist, she was a different pony with a different perception of the world, so the way she used that ability was different from him. Mist tended to be less mobile, relying on his mist for defense, while Fluttershy never stopped, always attacking from different heights and directions.
Their use of enchantments was also different. Mist tended more to use simple concepts such as direction and reflection, while Fluttershy frequently put together enchantments that were related to things like precedence and insanity.
Their battle was unsurprisingly equal, both of them spending nearly equal amounts of time attacking and defending. And it was a complex battle, fought in two different fronts at the same time: There was the merely physical fight, in which both of them tried to get through the defenses of the other and destroy their bodies, and there was the battle of wills, in which the two of them used dangerous enchantments with mental effects on each other to try and defeat them without needing direct attacks.
Mist made Fluttershy blind, and she retaliated by forcing him to sleep. Fluttershy made him feel as if somepony was squeezing his heart, and he retaliated by making her believe she had lost her wings.
Fluttershy would have died already if she hadn't received training in mental defenses, but even with that, the enchantments were applied directly and thus were much more effective than normal mental attacks. She could shake them off quickly, but they still managed to affect her somewhat. And of course, Mist himself was also very good on the side of mental defenses as well.
But things couldn't remain in balance forever, and as frequently happens in these situations, it was will that tipped the scales. Fluttershy caught a glance of Twilight on the other side of the room and got a new burst of strength, which also gave her an idea on how to finish things.
So she did another enchantment, this one an enchantment of pure emotion. Empathy was Fluttershy's core, so she pushed a big part of herself into the enchantment, forcing Mist to feel her emotions. And the construct, not being a true being, was overwhelmed by the tide of emotions for just long enough.
Fluttershy wrapped her mist around that of the enemy and found the weak spot, the point he was using to be able to breathe. Her mist rushed through the gap and pierced through the enemy's head.
Fluttershy waited a beat and then relaxed, feeling her own Soul Emulate cancel itself as the enemy died. She was able to see the remnants of his body disappearing into the light as her own mist faded. Then, she looked at Twilight.
She flew towards her and landed nearby. Twilight smiled at her.
Fluttershy couldn't contain herself anymore, she rushed at Twilight and wrapped her up in a hug.
There was a lot of discussion about whether it was really worth using such a dangerous plan. But Sunset managed to calm all of the others down by asking if they had any ideas with a good chance of working that were any less dangerous. When nopony managed to bring up a suggestion, they shifted towards discussing specifics about the plan, with every one of the other Knights deciding that, if they couldn't prevent the two from taking those risks, they should at least make sure they were as prepared and protected as was possible to be.
First were the protection spells. Dozens of the most advanced ones were cast on Sunset and Dash, and Applejack used her Eyes of Truth to look at their weaknesses and help adjust the spells into being perfectly specialized for enduring the attacks of Flames of Annihilation. For most purposes, this wouldn't be useful, either because such a level of defense wasn't necessary, or because the enemy would simply use different spells, but the situation they were in was definitely one in which this would help. Rarity's help was also needed in order to create a resonance between the new spells and the armors they already used for protection.
After that, Rarity proved her ability by creating two small artifacts on the spot. They were ice necklaces, made using the water Rarity had been using with her Water Ruler Sword. They were filled with magic and runes were engraved on them, and their goal was creating a barrier/heat shield that would also reduce the power of the enemy attacks. Rarity called them a "rush job that she wouldn't accept on normal circumstances", while the others thought they looked pretty good and their effects were impressive, so that was just Rarity's perfectionism acting up again.
Pinkie Pie was a surprise. Apparently she and Twilight had been working on a way to infuse others with chaotic energy that they could use in a reliable manner, and of course, the hardest part of all that was the word "reliable", they had been working with Fluttershy to make sure that ponies with chaotic attributes were capable of using it. They weren't at a point of the research where it could be said to be "complete", but there were already enough results that Pinkie felt that Sunset and Rainbow would be able to make use of it a single time. She did the procedure on them very carefully and put the energy in a dormant state, saying that they would have to use their will to activate it and make it do what they wanted.
Finally, Trixie cast a few layered illusions on them that, when the time came for the two to be attacked, would trick Flames of Annihilation into hitting them with only the edge of her attacks, instead of them needing to endure a direct hit.
The fact that, even with all those counter measures, neither Sunset nor Rainbow Dash were completely confident, really showed how much of an impression Flames of Annihilation had made on them.
And then they had to take care of the other preparations, of which the most important was the construction of the great magic circle. Every one of the Knights helped with that, and then all of them tried to prepare themselves for the critical moment of that crisis. They would never forgive themselves if something bad happened because they hadn't been ready enough, so they all felt the time passing quickly as each of the Knights did their best to achieve the highest level of ability that they were capable of.
And then their enemy appeared in the horizon. Still walking at the same speed as before, but now carrying along a true world of fire that created an almost apocalyptic scene.
The Knights waited at a relatively safe distance as Flames of Annihilation entered into the zone of the circle and slowly walked towards the center. And when she got there, the circle activated, shining brightly and resonating with the enemy. A circle of light seemed to dive into her body, and she hesitated for a single instant before continuing her movement.
"It's done. It worked." Applejack confirmed.
That was the signal for the plan to be put into action. Sunset was riding Rainbow Dash as she flew straight at Flames of Annihilation. The two charged magic quickly to have enough for their defenses. And they were also using their super modes again in order to get every single bit of advantage they could.
Pinkie Pie threw a powerful chaotic sphere that she had been charging for a while over the two of them. Rarity used her Earth Ruler Sword to create earth barriers right in front of Flames. They did their best to reduce the impact.
She attacked, with a huge burst of fire that completely destroyed Pinkie's chaotic sphere and Rarity's barriers. But the illusion worked, and the two Knights were only at the edges of the attack when they made contact.
At the last moment, both of them activated the chaotic defenses on their bodies, and their defensive spells also activated, along with Rarity's artifacts. The two of them also channeled every single bit of power they had charged into their armors and auras, creating the best possible defense they were capable of making.
But when contact was made, they discovered that they had still underestimated the power of their enemy.
The high energy chaos was melted while being able to have very little effect, the combination of defense spells and armor held up for an astonishing half a second and finally the two were able to feel the power of destruction on their own bodies, protected only by their aura defenses, which ended up shattering completely.
Both ponies were flung backwards, burns over their whole bodies from the fire, and other myriad injuries caused by the presence of the destruction concept that tried to bring an end to them in every way possible.
But they landed standing. The two were covered in injuries, their armors were completely destroyed, and they stumbled and vomited blood, but they were still conscious.
And a sensational power exploded from within them.
"Critical Mode!/Crisis Mode!" They announced together, and the last part of the plan began.
Those were abilities that Sunset and her apprentice had developed together. The initial idea was, considering that they would inevitably get hurt in their missions, could they find a way to get stronger due to the injuries, instead of weaker. This could seem impossible, but there were precedents, like the Prevail spell of Knight Kind Water, the Alchemist of Runes. Essentially, it was a way to turn their own injuries and pain into a sort of magical sacrifice, and as expected, it really wasn't something simple and straightforward, there were lots of rules and restrictions they had to accept to make it work.
Eventually, the two had success in creating versions of that ability tailored to themselves. However, they still shared many things, including the most important rule: The power they gained could only be used against whoever or whatever had caused the injuries on the first place.
Sunset's version of the ability was Critical Mode, and it was definitely well suited for her. It was an ability that synergized well with her Trance Mode, since it also increased the amount of power she could have access to all at once. The two energies mixed together to create a raging red glow. That power wasn't inferior to that of an Overdrive, but that kind of layering abilities could not be used excessively in order to avoid injuring the body permanently.
Rainbow Dash on the other hand, had a more subtle ability. Her Crisis Mode was created as a way to maximixe the effects of her instincts. Instead of simply giving herself more power, the Crisis Mode actually enhanced her senses beyond their limits, specially the magical sense, which also synergized well with the EX-Mode (since it also improved the senses), and with a greater awareness of the world, Rainbow Dash would have more information for her subconscious to put together into her instincts. Her glow was similar to Sunset, except that it was purple and seemed to include small lightning bolts.
And then Trixie did her part.
"Perfect Illusion: World's Obssession!" She cast her previously prepared spell.
It used an amount of power far beyond any of her other illusions, since it had to get through the passive defense of the opponent, to the point where it definitely wasn't good for any other situation. But for that one, it was perfect.
Flames suddenly had the absolute impression of Princesses Luna and Celestia being behind her.
She did not snarl, her face didn't change expressions, but she released so much power all at once that even the Knights who were far away had to use aura defense to protect themselves from the side effects of the spell. The only possible comparison would be the fall of a meteor, given how amazingly destructive were the flames she sent behind herself.
And of course, expending so much energy all at once meant that Flames of Annihilation didn't have a lot of power left for defense, so that was when the two Knights struck.
Rainbow Dash looked at Sunset and talked to her using the eye language, in a way that was much more fluent than she had ever been capable of. And she sent some pretty specific spatial instructions via that, before taking off at supersonic speeds.
She channeled her Sonic Rainboom into a sphere and shifted its magic into the destruction type. After all, she had a great example of a user of destruction magic that she had been seeing for a while and was still right there, so she just had to copy it. After that, she slapped the sphere and sent it straight at Flames.
That was when Sunset acted, she teleported directly to the place Rainbow had told her, in the exact moment she told her. It was the perfect place, since Rainbow had deliberately left a gap on her energy that allowed Sunset to take over the spell herself upon reaching there. This was an extremely quick and delicate operation, and then there was just one more thing to do:
"Septuple Magic Enhance: Heart Destroying Will!" Sunset enhanced the magic.
It took a phenomenal amount of power. So much that both her Critical and Trance modes were canceled out due to the sheer effort that took. This was definitely the strongest spell she had ever created, this was the greatest collaboration of master and apprentice.
There was neither sound nor light, as every scrap of energy of the spell was consumed only to harm Flames. And her heart was totally destroyed.
She stumbled and fell to the ground, stopping her walk for the first time.
Then her magic pulsed. Once, twice, three times. And her flames seemed to burn with even more intensity for a moment.
And, impossibly, she stood up.
Her eyes were open and once again she was no longer looking at her destination. Everypony could see the hole in her body where the heart was supposed to be, and they saw tendrils of magic forcing the blood to flow even without a heart. Applejack was the only one who really understood.
'No self... She considers even her body and life as tools... Since she had no self, she doesn't consider the heart as the origin of her life, and so she could survive...' Were her thoughts.
Flames of Annihilation looked around and took sight of each of the Knights.
"I remember... Enemies should be annihilated."
She spoke without emotions, but suddenly all the Knights felt a devastating sense of oppression. It looked like they had graduated from being obstacles to enemies, and she really wanted to kill them, so her very magic was trying to crush their existence without the need for any spells.
And yet, that was not the scariest thing. For she then opened her mouth again and started to chant:
"I am power purified...
My body is a channel for the fire of my will..."
Sunset understood immediately what was going on, and she went white.