Kayn continued using his altered Dragon's Breath for a full five minutes before letting it sizzle out. He had used a decent amount of mana casting and maintaining it, but nothing in front of that blast should have survived, not even someone as powerful as Polix.
However, contrary to Kayn's beliefs, as the dust and smoke settled, Kayn witnessed a grotesque body reforming extremely quickly right before his eyes. Within only a couple of seconds, Polix was standing there laughing.
"Hahaha! It worked! I knew this should have been something I was born with! That phoenix I had hunted all those years back was worth it in the end! You see Kayn, you cannot kill me! I have the heart of a phoenix now! My regeneration capabilities are unmatched! Now the real battle begins!" Polix shouted before launching himself at Kayn like a rocket.
Kayn wasn't expecting Polix to engage him in close combat, but he welcomed it none-the-less. Polix cast several spells as he flew towards Kayn, forcing Kayn to deflect or defend against them one after another until finally they collided. Polix's strength was astonishing and took Kayn by surprise once again as he was launched back through several already ruined buildings.
"IS THIS ALL YOU'VE GOT YOU INSIGNIFICANT BRAT?!" Polix yelled as he quickly caught up to where Kayn should have landed, only to find nothing but dust.
"Not even close." Kayn's voice came from the side of Polix as a fist coated with darkness and gravity smashed into his head, instantly caving in part of it as the Polix flew away like a rag doll across the broken city.
As Kayn expected though, Polix was soon standing and cracking his neck as his head ballooned back out and the injuries to his body from smashing into things quickly healed. Truly, whatever they did to ingrain the phoenix heart into this man was incredible, albeit highly unethical, but the results were quite the feat. Kayn could only guess that Envy had something to do with why the experiment succeeded in the long run, but it wasn't something he wanted to look into.
Then something happened that Kayn did not expect as there was no signal from his Mana Sense, a massive and sharp Earth spike jutted out from the ground behind him and speared him through the gut, sending his body high into the sky and towards Polix's next spell, a massive boulder sent down from the sky towards the ground like a meteorite.
Kayn grit his teeth while activating the Tethers of the Void as he wrapped the Mana Threads around the meteorite. Just before impact he tore the boulder asunder only to find Polix right behind it. He punched Kayn with so much force that his body was sent spiraling down the spear of earth he was previously impaled on.
As his body neared the bottom of the spear, Kayn's legs were detached from his body and he was split in two. When Polix saw this, he couldn't stop from laughing at his easy victory, but then it was his turn to be surprised. Pitch black tendrils extended from Kayn's torso and legs, reaching towards each other and quickly pulled themselves together. A bright white glow then covered Kayn's body as he healed fully on the spot.
"How? How can you do that!? Why were you born with something so powerful?" Polix yelled at Kayn as the envy of Kayn's prowess grew deeper in his heart.
Kayn felt the pull on his being becoming stronger, but it still wasn't enough to work on him just yet. What worried Kayn was the fact that this fight was going to be much harder than he anticipated. Polix was moving faster than even he could and his spells were being cast without any indication that they were happening.
The more Kayn thought about it, the more he didn't think he should be this out-matched. With all of his bonuses and the trials he had gone through, Polix should be an even match-up at worst!
"You look confused child. Just know that you never had a chance at winning this fight. My Sin, Envy, has an aura that will slowly but surely deplete your strength even if you can't feel it. While you may be able to keep your strength from transferring to me, you will still grow weaker when in my presence regardless. This is something even your strong soul and Sin cannot negate!"
Kayn stood in stupefaction, how big of an arrogant idiot was this guy? He just gave Kayn the answer to winning this fight, or at the very least being back on even ground!
Kayn looked deep into his soul where Kindness was currently sealed and released just a small portion of it to surround his body with it. The emotions transferred into his mind tried to tell him fighting was unnecessary, but Wrath and Kayn's desire for revenge overpowered the desires of Kindness.
Kayn felt the strength he didn't realize was being sapped from the very beginning return quickly once the aura of Kindness negated Envy. What better way was there to negate a Sin than use the opposing virtue against it? Kayn had learned this with Wrath and Patience, and he was just lucky enough to have obtained Kindness on Earth. Maybe this is the future Clementia saw, and why she wanted to give it to him, foreseeing that he would need it.
Polix noticed something different about Kayn as he straightened his back and wings while staring up into the sky at him, but he couldn't tell what was happening as he had no clue about the Virtues.
All of the sudden, several elemental balls began to swirl around Kayn. Every main element and several deviant forms all swirled and changed shape into various swords.
Kayn, who had his eyes closed during the process of summoning and creating all of these swords finally opened them to look at Polix before he spoke, "Eternal Blade Art: Elemental Sword Domain."
Every single one of these swords would be a one-time use, but Kayn's Sword Aura was able to be infused into them as well as having been created from elemental infusions of Sword Aura itself. This was an untested technique that Kayn only recently integrated to his mind and body thanks to the avatar in the Wanderer's Villa, but this was the perfect time to test out how effective it would be.
Polix felt weary when looking at the swords surrounding Kayn, but he was confident in his own strength, not to mention he was also confident in Envy slowly sapping away Kayn's strength. Not wanting to wait for Kayn to make the first move, he created several boulders and spears of earth and wind and launched them down towards Kayn at insane speeds.
Kayn calmly grabbed the lightning blade he formed as he took a stance, and slashing upwards at the incoming spells and Polix himself. "Sword Art: Heaven's Sundering"
Polix watched in horror as a massive arc of lightning swept through his spells and hit his body before he could even move. His left arm was split from his body, but this only caused him to get angry as he snarled and pushed mana into his new phoenix heart, regenerating his missing limb the next instant.
With his All-Seeing Eyes active, Kayn smiled as he knew how he was going to defeat Polix. He could do it quickly by pouring every ounce of his mana into void fusion elements, but that wasn't what Kayn wanted. He wanted to make Polix feel fear. He wanted him to beg for his life when he realized that his end was coming. This last attack and regeneration cycle gave Kayn the perfect idea of how to realize his goals.
Polix had an absolutely massive mana pool. Not quite as much as Kayn and he couldn't gain it naturally like Kayn could, but it was still a massive amount regardless. However, every time he had to regenerate himself, his mana pool would drop by a good amount rather than the tiny amount he was using for his spells.
Kayn's plan then? Tear him apart and let him regenerate until his mana pool was exhausted. Then when he was finally on the ground crawling and begging Kayn for mercy, he would deliver the finishing blow. This meant he would need to avoid piercing Polix's mana core, but that wouldn't be too hard as all he needed to do was focus on his limbs and head on occasion.
Grabbing the lava elemental blade into his hand that was undulating due to being in a liquid state, Kayn launched into the sky towards Polix. Polix seeing this knew that he had underestimated this young man again. He pulled out a legend grade spear from his dimensional ring before coating it with his earth and wind mana, much as a magic warrior would.
Polix was skilled both as a mage and magic warrior, mostly due to Envy, but he developed and honed his skills over the years. He was going to confront Kayn as both now that things had gone this way.
Thus, an epic battle of sword and spear began. Polix was stuck on the defensive as he had to block all of Kayn's attacks with his own spear while simultaneously casting spells around his body to deflect or block the floating elemental blades.
Polix was initially ecstatic as every time he struck the sword in Kayn's hand with enough force or one of the floating blades failed to penetrate his defenses, they would vanish. But his hope was soon dashed as another blade was soon summoned to replace it.
What Polix had failed to realize was that as long as Kayn kept the Elemental Sword Domain active, the swords would always come back. He would soon learn that they could be summoned anywhere within a large area around Kayn, not just behind him.
Kayn swung down with the earth and fire blades he summoned which exploded upon coming into contact with Polix's spear, but suddenly the wind elemental blade appeared behind Polix without warning and sliced his left arm off again.
Polix snarled as he saw Kayn smirk, he wasn't nearly done with this arrogant brat. His arm grew back within a second and the fight continued on like nothing happened.