A/N: I find myself more interested in Kristen Verne's KH Universe than my own. But don't worry this story isn't dead by any mean. Speaking of Kris, I'd like to thank her for motivating me into getting this chapter done, as well as for her...input regarding a plot point that's coming up.

Anyway, as the title has probably hinted, this chapter mostly focuses around my interpretation on how one particular character became another's arch enemy.

Fallen Angel

KAI: It was the day when one of the town's greatest idols suddenly jumped off his pedestal.

Xehanort, Braig and Even were standing by one of the lab's containment cells. From inside the cell, shouts of agony along with a lot of hard banging could be heard.

"Yeesh!" said Braig. "I think you broke him."

"Clearly the boy didn't have the fortitude for such a strenuous trial," said Xehanort. "It might take some time for him to...adjust to this."

Even was writing some notes. "Still, it looks like we achieved the goal of this experiment. So I would say that Project Reptile is a success. Wouldn't you agree, Xehanort?"

"So it would seem. But giving how unstable he is at the moment, we'd better keep him under close observation, just in case an unfortunate side effect occurs that would reclassify this experiment as a failure."

"Yes sir."

Xehanort then walked over to his desk. "We'll probably need to fine tune the process of cracking open the heart's darkness and molding it into a more physical form for future procedures, but now we know it's possible to give a person a Heartless-like trait without actually turning them into a Heartless."(1)

"So," said Braig, "Now that we're done with him for now, what's next?"

Ansem's apprentice began searching one of his folders. "I have a couple more related experiments in mind." He then pulls out one of his notes. "Like this one for example, Project Seraph."

Even looked at the notes. "Oh ho! Fascinating! Such an enhancement would be any soldier's dream."

"Indeed. Though this time I would like a more durable subject."

"What do you mean?" asked Braig.

"Ryu was a bit on the weaker side. So for this experiment, I want the subject to be far stronger. I'd like to see what happens when I add to an already powerful soldier."

"Well," Even chuckled, "aren't we ambitious! If it's a powerful subject you want, I think we all know who the perfect candidate is!"

"Indeed. All we need is to convince him to undergo the procedure."

"You just leave that to me!" declared Braig. "I think I know how to sweet talk him into it."

"Come again?" asked Sephiroth.

"You heard me," said Braig. "Xehanort is putting together a little soldier enhancement project for the Castle Guard. And we want YOU, the Captain of the Guard(2), to be the first to test it out."

Sephiroth is silent for a moment before replying. "Not interested."

"Aw, why not?"

"Why do I need more power when I'm already the strongest?"

"Oh come now, don't be like that. This is not just for you, you know. It's for the whole guard. It's a very delicate procedure, and we wanna make sure its safe. And being the strongest in Radiant Garden means you have the best shot at undergoing it without as much risk."

The guard captain glared a Braig skeptically. "Did Lord Ansem really approve of this project?"

"Of course he did," the sharp shooter lied. "And even he agrees that you're our best option."

"Well good to hear that you have so much faith in me. But I'm no one's lab rat."

"Well think of it this way. Would you rather I give to someone like, say, Zack for example?" Braig smirked at how Sephiroth's eye narrowed at that. "Yes. You've noticed it too, right? How Zack has be drastically improving since he returned from his little training trip. He's really been catching up to you. I'd even go as far as to say he's your close second already. If he keeps this up, it'll only be a matter of time before he surpasses you. Now imagine what would happen if we gave him the enhancements and it worked."

Sephiroth looked away in thought. While the man was never really one for glory, he had always took pride in his superior strength among the guard. So the idea that someone could surpass him in such a way didn't sit well with him. True, he enjoyed a challenge when one presented itself, and Zack has been quite a challenge in their spars, but the thought of being vastly inferior to someone else was a real blow to his pride.

The one-eyed soldier chuckled as he decided to add more salt to the wound. "But he's not the only one you need to worry about, is he? I've noticed you've had your eye one particular recruit, Cloud. He has been showing a lot of promise lately, hasn't he? He's been breezing his lessons like nothing, and winning his spars like a champ. And the fact that he's close friends with Zack only adds to his potential. And then there's our youngest recruit, Kai. Boy is that squirt starting to scare me. They don't call him a prodigy for nothing. Sure sometimes he starts his lessons off a little rocky, but he always manages to find a way around his roadblocks. There's really no telling when he'll stop surprising us. I mean, you saw the damage he did to the waterworks, right? A thirteen-year-old did that after going berserk. That proves how powerful that kid can be. Not to mention the fact that he's the son of Suzaku, the only soldier you ever considered an equal."

Sephiroth stood there silently in contemplation.

Hook, line, and sinker, thought Braig. "Come on. It's for the Castle Guard."

After another minute of silence the captain said, "So when is the procedure?"

"Give Xehanort a couple more weeks to fine tune a few things and we'll get started. I only ask that you keep quiet about this. Some people might get the wrong idea."

The recruits were in the outer gardens for their training session.

Kai was sitting on the ground with a bottle of water. Zack had told him to take a break from sparring matches. The boy sighed as he looked at the sky. It had been a few weeks since the incident with Ryu. Using the power of darkness and inadvertently hurting Kairi was still haunting him. While she has recovered and has forgiven him, he still hasn't forgiven himself for what he did. Still, knowing that what turned out to be the one thing that caught Ryu off guard, he couldn't help but wonder what would've if he hadn't used that power, but at the same time wondered why it was necessary.

The idea of there being darkness in him, just waiting to be unleashed at any point he is compromised, really frightened him. He wondered how the darkness could've been so strong in him. He heard Merlin's theory about it and he couldn't help but wonder if it was true. Was the pain he had been going through in his life really been a factor? Had he really been too hasty in his quest for power?

... Was that incident fate's way of warning him of what could happen if he continued to rush carelessly to get stronger? Who could say?

Kai couldn't help but look at his sword, Muramasa, and notice that the normally lightish red blade had become a darker tint since the incident. Why that was, no one knew for sure, but the boy surmised that he had inadvertently stained it with his darkness. However, it seemed to still function normally, so there didn't seem to be any harm in it, other than maybe being a subtle reminder of what he had done. But one thing he was certain of now...there was no way he was getting a Keyblade. He had ultimately given up on that endeavor. After unleashing the darkness and hurting his own sister, he could see now that he just wasn't worthy to wield one. Maybe Aqua's little recital had no effect on me after all, he thought.

Whatever the case, Kai still hasn't given up on his desire to get stronger to protect his sister. He's just decided to mellow down a little, approach this more carefully. He certainly didn't want what happened at the waterworks to repeat itself. He has made some new strides since then though, namely discovering his ability to combine his Spellblade art with his Sonic Wave attack. He felt he was finally making significant progress in using magic properly, to the point where he could at least cast a small fireball without it blowing up in his face, though its power still needed work.

Kai looked over at a sparring ring to see their supervisor, Zack, having a little one-on-one with Cloud. Kai couldn't help but smirk at the two. Apparently those two were long time friends. One would say that Zack was like older brother to Cloud. When Zack left on his training trip, Cloud was always worried about him, and when Sephiroth retrieved him, the younger swordsman was relieved. It was an interesting bond the two of them shared. Even after Zack was promoted he continued to support Cloud and encourage everyone to do their best, embrace their dreams, and defend their honor as castle guards.

The two clashed swords for a while, before Cloud fell to the ground in exhaustion.

Zack chuckled. "Alright. I think it's time you took a break."

"R-right." replied Cloud.

The supervisor walked over to a cooler, took out a water bottle, and tossed it to the recruit. "You really are improving a lot Cloud. Keep this up, and you'll be an official guard in no time."

Cloud took a sip of his water. "I wonder if I'll ever be as strong as you, Zack."

"Oh you still have a ways to go before you catch up to me. But trust me, I'm sure you can."

"I don't know. You yourself have been getting a lot stronger pretty fast. You're practically at the same level as Captain Sephiroth."

Zack chuckled again. "Don't let that discourage you. Remember what I keep telling you. All effort is pointless if you don't believe in yourself. Strength of will is key to strength of body. I know you can go far." He then turned to everyone else. "That goes for everyone else as well. Keep your spirits high, and never give up on your goals. Am I right?"

"Right." Everyone replied.

"Okay. Who's next?"

"U-um, Zack?" Zidane suddenly inquired while looking over the city walls.

"Yes?"

"Is there suppose to be smoke coming from the city?"

Everyone looked above the walls and there was indeed smoke. And a lot of it too.

Zack immediate grew tense. "That can't be good!" With that, Zack rushed into the town, with the recruits following suit to see what was going on.

When they entered, they discovered that half the town was on fire. But that wasn't all. They also saw a few civilians dead on the ground, along with several guards. It was a horrific sight.

A groan caught everyone's attention. One of the downed guards was alive, Laguna. Zack, Squall, and Lightning quickly ran to his side, with Lightning applying some healing magic on him.

"Laguna!" shouted Zack. "Are you alright?"

His only reply was a groan.

"Come old man, say something!" shouted Squall. "What happened here?"

Laguna then looked in a direction. "S...Seph...iroth...wh-why...?"

Everyone looked at the direction the guard was looking and saw Sephiroth standing right there among the flames looking down and holding his Masamune sword. But something was off about him. For one he had a noticeable dark aura around him, but what was much more noticeable was...he had a dark wing sprouting out of his back, over his right shoulder.

"Sephiroth?" asked Zack. "Wh...What are you doing?"

The captain only gave Zack a menacing glare before turning around a walking through the fire. (3)

Angered by the lack of response, Zack took his Buster Sword from his back. "Kids stay here and alert the rest of the guard." He then charge in the direction Sephiroth was heading.

Three of the recruits, however, did not listen to orders. Cloud, concerned about his old friend, almost immediately went after him. Tifa, concerned about Cloud, followed suit. And Kai, concerned about the darkness Sephiroth exuded, pursued last. The others tried to stop them but ended up roadblocked by fallen burning debris.

The three recruits soon found themselves atop the town's Reactor. They hid themselves as Zack approached Sephiroth, who had his back turned.

"Sephiroth!" Zack shouted. "What's going on here?" He received no reply. "Answer me! Why did you attack the our home? Why did you attack your fellow guards? What kind of captain of the guard does this?!"

After a brief moment of silence, Sephiroth finally replied. "Zack Fair." He then turned around and pointed his sword at Zack. "I need you... to test the limits of my new power."

Zack readied his own blade. "Sephiroth! Have you lost your mind?!"

"Come! Fight with ALL your strength!"

After a moment of pause between the two before the charged at each other and started clashing swords. Zack was struggling to keep up while Sephiroth looked like he was barely working up a sweat. Zack then jump back and casted three Firaga spells at Sephiroth, which seemed to hit dead on, but when the dust settled, it was like they didn't hit him at all.

Sephiroth then raised his arm, "Hellfire!" he called as pillars of fire began bursting from the ground beneath his opponent.

The Buster Swordsman was able to evade those pillars, and then charged energy into this sword. "Blade Beam!" Zack shouted as his launch a vertical shockwave along the ground. The captain merely deflected the attack with his sword.

The three hidden recruit watched as another round of sword clashing ensued. They all couldn't take there eye off the battle. They were in awe at both of their strength, but were also very nervous at Sephiroth's power.

Soon Zack leapt into the air. "Meteorain!" He swing his sword and launched six small meteors.

Sephiroth then waved his right arm, his wing moving with it. "Shadowflare!" And six orbs of darkness appeared, each blocking a meteor, exploding on impact.

"Is that all, Zack Fair?" Sephiroth said coldly. "Surely you can do better than that."

Zack grew angry as he began to gather an immense amount of energy through his body. Sephiroth smirked at this as he did the same but with a mixture of darkness. The recruits could just feel the power the two of them were exuding. They could tell they were pulling out all the stops.

"Omnislash!" shouted Zack.

"Octaslash!" called Sephiroth.

The two of them flew into the air as they began clashing repeatedly at lightning speed. The recruits could barely follow their movements. But before they knew it, Sephiroth suddenly flew past Zack, who found himself with thirteen cut on this body, before plummeting to the ground.

"How disappointing." said the crazed captain. "And here I thought you had what it took to eliminate me. But that was barely even a dance."

The younger guard struggled to get up. "S-Sephiroth!" He then coughed "Wh-what happened to you!?"

"I have embraced the darkness. It has shown me my true desires. Power to destroy whatever I see fit. Worthy opponents capable of pushing me to my limit."

"Y-you would throw away your honor as captain of the guard for that?"

"Honor. A word that would only be used by a puppet that allows the others to pull their strings. But I refuse to be a slave any longer. This world has nothing more to offer me. It is time I left it behind."

Zack managed to push up on his arms but still struggled. "Oh no you don't! Not if I have anything to say about it! "

"You were a worthy opponent up until now, Zack." Sephiroth approach the downed guard before raising his insanely long katana high. "But now you are nothing." He then proceeded to bring his sword down upon Zack...

...Only for Cloud to suddenly appear between them and blocking with his longsword.

"C-Cloud?" the injured guard watched as his friend struggled to keep his ground against Sephiroth.

The traitorous captain then spotted something at the corner of his eye. Tifa had leapt up bringing her metal clad fists down onto him. Sephiroth ceased his attack and evaded Tifa's punch. He then deflected a Sonic Wave sent by Kai. He then glared at all three.

"Wh-what are... you guys doing!?" Zack weakly shouted before coughing. "G-get out of here! You can't-"

But Cloud wasn't listening as he charged at Sephiroth. He crossed swords with the captain, but he struggled to push back the man who held still as a statue. Tifa tried another leaping punch, only for the silver-haired man to catch her fist like it was nothing and tossed her aside. Kai then tried to flank him, which prompted the captain to kick Cloud away before deflecting the youngest kid's attack. Both young swordsmen attempted to attack again, but Sephiroth raised his insanely long katana to the side, prompting the two to block instead. When the traitor swung his sword at them, the two felt their swords being hit seven times in rapid succession, before the last hit push them back again.

Tifa then casted a blizzard spell, however it was as if it hit an invisible barrier. Confuse as to what just happened, the girl casting it three more times. At the same time, Cloud casted several fire spells while Kai activated Thunderblade and launched a lightning coated Sonic Wave. It was the same result, their magic had no affect on him.

The three continued to try and take down Sephiroth, but they couldn't land a single blow, and he wasn't even trying.

Soon the captain threw Tifa hard into a wall. Before she could recover she suddenly found three of Sephiroth's Shadowflare orbs. She let out a scream as the orbs promptly exploded on her, knocking her unconscious.

"Tifa!" Cloud shouted as he rushed to her side. He tried to shake her awake to no avail. "Tifa! Tifa!"

Kai then charge at Sephiroth, only for a small dark meteor to impact the ground in front of him, the blast sending him crashing into a wall and falling to the ground. Kai was struggling to even move.

Cloud readied his sword. However before he could act...

"Enough." Sephiroth said as he waved his glowing hand. "Descend! Heartless Angel!"

Cloud shouted as a dark glow enveloped his chest, causing him severe pain. He fell on all fours, clutching his chest.

By now, Zack had finally got to his knees. He tried to lift his Buster Sword, but in the state he's in, it felt a lot heavier to him.

Sephiroth then jumped high into the air, came over the blond haired boy, his Masamune positioned in a downward trusting motion. Zack gasped as Sephiroth started to come down onto Cloud. Summoning what strength he could muster he kicked himself off to shove Cloud out of the way.

Unfortunately this resulted in Zack receiving a stab from the back through his chest onto the ground.

Cloud watched in shock as his best friend used the last of his strength to toss him his Buster Sword before the light left his eyes. "ZAAAACCCK!" he cried out.

"How pitiful," Sephiroth said coldly. "A slave to his emotions, just like everyone else. Those who submit themselves to others only weigh themselves down. They only ever get themselves killed."

"SEPHIROTH!" Cloud shouted in anger as he threw his longsword at his friend's killer, who only deflected in away. He then grabbed Zack's Buster Sword and stood up in anger, a dark mist surrounding him. He then charged at Sephiroth and began clashing swords. The sword was heavier than he was use to, but he managed surprisingly well. Unfortunately it wasn't enough, as his opponent wasn't breaking a sweat.

Soon they locked blades. "You know, Cloud Strife," the traitor said, "out of all the recruits, you've always been the one that interested me the most. You show so much potential, even more then Zack. Perhaps one of these days, you'll have what it takes to eliminate me.(4)"

Cloud then leapt back and charged energy into the Buster Sword. "Cross-slash!" He swung his powered up weapon three times, the first two were evaded, while the third one was blocked easily.

Sephiroth suddenly grabbed the Cloud by his face and proceeded to run dark electricity through the boy's body. "I could kill you, but I'm more interested in seeing you grow stronger. Cut all your ties. Don't be their puppet. Foster your hatred. Break your limits. Give into the darkness. And when you are strong enough, come seek me out... and give me a real battle."

Cloud then collapsed from pain and exhaustion before the traitor tossed him into a wall, knocking him unconscious.

"You monster!" Sephiroth turned to see Kai shakily standing up. Traces of black mist emanated from the redhead's body as a pained but angered look was plastered on his face.

"Ah, I had almost forgotten about you," the turncoat captain sounded almost bored. "You know, Kai Hikaru, out of everyone I've met, I think you have to be the biggest puppet of them all. You willingly make yourself a slave to almost everyone in this town, never truly thinking for yourself."

Kai readied his sword. "Shut...up."

"But you know what I find even more pathetic? The fact you especially allow your strings to be pulled by, more than anyone else, a helpless little girl."

"I told you to SHUT UP!" With that Kai's rage once again unleashed his power of darkness, surrounding himself in an intense dark aura.

Sephiroth just looked on in intrigue. "I see. So this is the power that damaged the waterworks and defeated Ryu. I must admit, your darkness is quite strong for one your age, and for one who lets it run wild as you do. It's no wonder you were able to defeat Ryu, who unlike you had accepted the darkness."

Kai yelled out as he launched a dark-coated Sonic Wave. Only for Sephiroth to merely wave the projectile away with his hand.

"But Ryu was a novice compared to me. In the face of a superior like myself, your power is nothing without proper control."

Kai then let out a roar as he leapt toward the traitor with Muramasa ready to cut him down... only to receive a hard punch in the gut, knocking the wind out of him and causing him to drop his sword, and then find himself in a choke hold.

Sephiroth just stared at the boy. "I'll admit, your father was the only one I once considered an equal. It was truly a shame Zabuza blindsided him. But quite frankly, boy... you don't interest me anymore."

And with that Sephiroth just tossed Kai before quickly swiping his Masamune, leaving a deep cut across the boy's chest. Kai let out a brief gurgled gasp as he cough up blood. The pain was so excruciating he couldn't let out a sound. His body stiffened, his vision blurred, the taste of his own blood came into his mouth, and the only thing he could hear was the echoing sound of the very strike he received.

The world around him felt like it was moving in slow motion as he flew over the railing and into the pit below. He could only think of his sister, Kairi, as he silently plummeted into the abyss.

Sephiroth only watched coldly as the young prodigy swordsman fell to his doom. "I'm done here," he said to no one in particular.

Dilan, Aeleus and three guards, led there by Lightning, arrived just in time to see Sephiroth walk into a dark portal, which closed upon entering. Immediately, they went to check on everyone the area.

Aeleus went over to Cloud, checking for vital signs. He sighed in relief. "Cloud is alright, just unconscious. But he needs treatment right away."

"Same goes for Tifa," said Lightning.

Dilan however let out a sad sigh. "I'm afraid...Zack wasn't so lucky."

Aeleus slammed his fist onto the ground. "Blast! How could this have happened?"

Lightning started looking around. "Wait...where's Kai? He was suppose to be with Cloud and Tifa." She then spotted Muramasa on the ground near the railings. "Oh no!" She then grabbed the katana before looking over the edge, unable to see into the darkness below.

Dilan then turned to the other three guards. "You two, take these kids to the infirmary. And you, call a search party! We have a missing person!"

From the window into her room in the castle Kairi watched in horror as half the town was on fire. She cuddled her kitten into her arms. She was scared at what she was seeing.

But that wasn't all. She had been having a really bad feeling. She couldn't help but feel that something else...something terrible had happened. Her thoughts especially lingered on her brother.

"Kai...please be okay!"

KAIRI: If only I knew in that moment what had happen that day. If only I knew...what would become of my brother.

Meanwhile:

"Man, oh man!" exclaimed Braig. "Talk about going mad with power!"

"Indeed," replied Xehanort. "Sephiroth had great pride in his strength. He desired to be the strongest soldier alive. That proved to be the weaknesses that allowed us to convince him to undergo the procedure. However he had another weakness, a desire for a real fight, a fight to the death. It appears that the experiment brought out that inner desire and heightened it to its maximum."

"Well enhancing his strength was definitely a success," Even stated. "I am a bit disappointed that we only gave him one wing. Project Seraph was aiming to give him six."

"Perhaps he'll gain more wings in time.(5)" said Xehanort. "Regardless I'd call it a success."

"But did you see the damage he did?" asked Braig. "That kind of incident is gonna draw unwanted attention, and some people are gonna start snooping around for answers on what the heck happened to him. We're lucky Sephiroth doesn't have a big mouth, or he could've ratted us out!"

"The casualties were most unfortunate," said Even "but such is the price to pay for science."

"And besides," added Xehanort, "the incident gave us the perfect opportunity to nab our next subject, the one I've been most interested in experimenting on, so it worked out in the end."

The one-eyed ruffian crossed his arms. "I know we put him in a stasis pod, but are you sure you don't wanna get a healer in here to make sure he stays alive?"

"For this next experiment, I want the subject to be on death's door. Why waste the opportunity?"

"The stasis pod will keep him alive until we're ready," Even interjected. "But I suggest we make haste with the preparations. After all, we can't keep him hidden forever."

Braig then scratches the back of his head. "You know, Lord Ansem is gonna be furious when he finds out about this one."

Xehanort chuckled. "Relax. If this goes as planned, he'll have no choice but to thank me. Now then, let not waste any time. Make preparations for Project Lycan."

A/N: And this folks concludes my interpretation of how Sephiroth became Cloud's arch enemy. And as for the last scene with Xehanort, well you can guess if you want, but you'll just have to find out next chapter.

Footnotes:

(1) I'll leave what exactly happened to Ryu to your imagination for now. Don't worry, it'll be brought up later.

(2) I have come to realize that I hadn't assigned the rank of captain to anyone. So I decided to just give it to the strongest of the guard.

(3) Sound familiar? XD

(4) You see, one thing about KH Sephiroth is that unlike his FF7 counterpart, he seems to have no interest in ruler/destroying the world. His line in KH2, "But it seem Cloud is the only one who can eliminate me," gave me the impression that he's only interested in having a real fight to the death, and believes that Cloud is the only one who's capable of providing him with such a challenge.

(5) I refer to the two additional wings Sephiroth sprouts from his hips in KH2.