Pre-Story Author's Notes:

I got my first story request! (or rather a barrage of them from one guy). One suggestion in particular caught my interest and got me thinking, a request for a "dark!Aqua". I contemplated the idea for a time, the Aqua we know in KH is a light-aligned, good-hearted, dutiful, and disciplined keybearer. An 'evil' version of her just didn't fit in my mind, but... as we know, Darkness isn't necessarily evil, Riku uses the darkness after all, and he's a good guy. As does Terra, he used the darkness, and while he was manipulated to hell and back by Xehanort, Terra WASN'T evil.

So the thought struck me...

Why not try taking Aqua down that path? Using darkness for the sake of the light, for her friends (at first...?).

The question then becomes... how?

The answer is easy enough: Master Xehanort.

But, the thing is, I don't want this to simply become a KH Birth By Sleep retelling with only Aqua and Terra's roles reversed, there's probably already one or two of those out there. I want something, more.

How/why you ask?

Aqua isn't Terra. She's not as gullible, and while Terra isn't stupid by any means, Aqua IMO is smarter. Not to mention, magic is her focus over raw strength, her talents are different. The story begins when Master Xehanort brings Ventus to Eraqus, and while it may cross paths with the actual KH lore at times, it will eventually break off and become it's own complete monster, stretching far past KH: BBS. The story will probably follow Birth By Sleep up until only a certain point (first time in Radiant Garden maybe?), before things start spiraling out of control. How exactly remains to be seen...

As a note: I reserve the right to alter and create lore to fit or further the Fanfiction (all rights/characters/ect of course belong to Square Enix to begin with). You will already notice a few changes in this chapter alone, as an example, Xehanort was already aware of Terra/Aqua before his visit to drop off Ventus. (This will in turn change how his Xehanort Reports are written).

For this story's sake: Kingdom Hearts Chi and everything relating to it (unions, lux, book of prophecies, ect...) is not taken into account. I will create my own lore for the Keyblade War for this story. KH: Chi is... just a bit to weird for me to handle, sorry. I may or may not incorporate ideas and concepts from Kingdom Hearts III when it's eventually released.

Anyway, without further adieu...

Aqua: Heart of Darkness

Chapter 1: Darkening Waters

Master Xehanort walked into the castle of Land of Departure, his silent, near comatose apprentice Ventus sullenly following aside him. His old fellow apprentice, now the master of this place, Eraqus stood at the steps to grudgingly greet him. Up above, he caught sight of his old friend's two apprentices staring down at them. Terra and Aqua their names were. He had seen them on occasion when he had come to visit Eraqus, or come to spy on him. They were progressing impressively, he had studied them, identifying them for the purposes they would one day serve. He had to resist the urge to curl his lips into a smile. Everything was slowly falling into place, all that was needed was time for his own apprentice to heal and grow strong.

The boy now behind him was part of the key.

The young man above him would be his new host.

The young woman would be the backup, to the key or the host, whichever was necessary if something went wrong.

Though, he held doubts she could serve as a host. From what he could recall of the girl during his 'visits', she seemed too disciplined, too aligned to the light. She was, as ever, Eraqus's dutiful apprentice. She had seemed like an emotionless cog of the light, polite, respectful, utterly bland. He hadn't seen a single thing he could use to turn her down a darker path, unlike Terra. That boy would be easy to manipulate.

"Xehanort? Why have you returned?" asked Eraqus, a little tense.

Oh, right. Their last face to face meeting hadn't ended well. Eraqus bore his scar rather well, he was faintly surprised the man hadn't healed it away. Perhaps he kept it as a reminder?

Xehnort closed his eyes and prepared his act. "Eraqus... I made a mistake."

Eraqus frowned, his eyes flickering to Ventus behind him. "A mistake?"

"We should talk in private," murmured Xehanort, briefly turning to Ventus, "Remain here, boy."

They walked off together, Xehanort took a brief note of Eraqus's apprentices moving to talk to Ventus. He dismissed the thought and turned to Eraqus as they approached the throne.

"Old friend...," began Xehanort.

"Friend?" questioned Eraqus bitterly, holding a hand up to his scar.

Xehanort sighed. "As I said, I made a mistake, many of them in fact. The last one was the final straw. I'm not fit to bear an apprentice."

There was silence for a moment before Eraqus spoke, "Your apprentice... seemed off... Xehanort, what happened? What is this 'mistake' you speak of?"

"He lost himself to darkness, the foolishness of my teachings, and I was forced to extract the darkness from his heart, forcibly," half-lied Xehanort.

Eraqus literally gagged. "Xehanort! Why?"

Xehanort looked away. "As I said my friend, I made a mistake, and now poor Ventus suffers for my foolishness. His memories gone, his heart..."

"Damaged," finished Eraqus grimly, "Xehanort... how could you let the darkness take him? How could you put a boy through something like that? "

"As I said, I'm not fit to bear an apprentice. I once told you my own darkness was not your concern, but, I see I was wrong, I should have listened to you. I don't deserve it, but, I ask, for old times sake, will you take him from me? Raise and protect him where I could not?" asked Xehanort with fake regret.

Eraqus closed his eyes and sighed, a conflicted look on his face. "I..."

They both spun as a pained cry filled the air. They rushed back to the entrance and down the stairs, sighting Ventus collapsed on the ground. Xehanort had been ready to take point and tend to the boy, when something caught his eye, or rather, his senses. A wave of emotions: fear and guilt. The sensation was so alien to him, not because he had never felt them before, but, because who they had come from. His eyes flickered to Aqua. He had to admit, this was more negative emotion than he had ever felt from her in all the times he had spied on Eraqus's pupils. He was tempted to ignore it and continue on to the boy... but... he decided to sit back and wait, curious to see how this developed.

"What did you do?" demanded Eraqus as he approached.

"Nothing... I...," began Terra, "I just asked him some stuff..."

Xehanort's eyes flickered to Ventus. Trying to gauge the boy's memories in such a weakened state had probably caused his heart an immense pain as it tried to recollect what wasn't there.

Eraqus sighed. "Ventus cannot tell you anything... because he cannot remember anything."

Aqua looked utterly crushed. "He... can't? Why? What happened? Why did he suddenly cry out and collapse?"

Xehanort eyed her curiously. There it was again, a surge of anxiety, fear, and guilt... hmm... interesting. Those feelings were tools he could use to shape her, the beginnings of darkness, should he choose to pursue it. Yet... why now and not before? He had observed the pair of apprentices on and off for years, so why now was this the first time he...

He watched her turn a worried look to Ventus, and then it hit him

Because those she cared for were in pain. She had just met Ventus, but Xehanort could see the worry and care she already had forming for the boy. He could practically feel the bond already starting. So that was it... he could poke and prod her soley all he wanted, but she'd never budge... never fall...

However...

Put her friends, or those she comes to care about in danger...

A brief smile touched his lips and he thought: "And she'll go to the ends of the earth to protect them, no matter the personal cost, she'd throw herself into darkness if it meant saving her friends."

After all, hadn't he done the same, the first time he had dabbled in darkness? Fearing for Yen Sid and Eraqus's safety? Yes, she could be used, far more than he originally thought. He sized up her abilities and compared them to Terra's briefly. Terra had more raw power, but, Aqua was by far the more impressive mage, and magic was something he himself had come to prefer as his body began to age and weaken. She was quick and agile as well, not as fast as Ventus, when he actually bothered to fight instead of cowering that is, but still quick enough. Her mind was sharp, and intelligent, and while Terra wasn't a complete imbecile, his matters of the mind and studies were a bit... lacking in comparison.

Yes... now that he thought about it, he shared a bit more in common with Aqua than he did Terra. Perhaps... she would make a better host. Though, the fact that she was female would be a curious change to adapt to. But then again, why not? He was chasing the legends of the Keyblade War to find his own answers, new experiences, a new life. When the X-Blade was in his hands and he begun the war anew, why not claim a new existence as well?

"What happened to him?" Aqua questioned.

It occurred to him suddenly he had been lost in his own thoughts. Eraqus had not answered, and all three of them were looking to him. How quaint, Eraqus wasn't going to tattle on him, even with his age, his acting skills hadn't lost their touch if Eraqus had truly bought it. He looked at Aqua for a moment, contemplative, before he made his decision.

The boy was part of the key.

The young man would be the backup, easily able to replace the chosen host or the dark half of the key.

The young woman would be the chosen host.

Turning her down a darker path would be a simple thing. All he had to do was simply draw her protectiveness out and use it against her. Her darkness he predicted would be weak at first, but oh how he would make it grow.

"I hurt him," Xehanort finally answered bluntly, watching for her reaction.

There was open shock for a moment, before anger splashed across Aqua's face, she took a step forward, fists clenched. "You... you hurt him?! Why? What did you DO to him!?"

Ah... there it was. What was usually so bottled up and kept hidden by her discipline was showing at last. He could taste the anger radiating off her, uncontrolled and untempered. That look on her face, her tensed body, clenched fists, she wanted to hurt him for harming Ventus. Keeping her emotions bottled up and restrained made it all the more difficult for the young apprentice to control them when they were unleashed. That was something he could use against her, all to easily. He used his powers of darkness, using it to subtly enhance her anger right under the nose of Eraqus. How easy it was...

"None of your concern," he answered her, looking at the door and starting forward, one eye and his senses kept on Aqua as he did so.

Driven by the enhanced anger, Aqua reflexively moved to keep herself between him and the unconscious Ventus, keyblade appearing in her hands, fury on her face...

"Aqua!" came the sharp tone of Eraqus.

Aqua flinched and turned her head towards her master, and when all of their attention was diverted, Xehanort struck again with his darkness, this assault more heavy then the last. Anxiety, paranoia, distrust, he found and magnified those emotions within her subtly, using them to dive further down into her unguarded heart. There, he found what he was looking for: Her darkness. All hearts had it, some far more or far less than others. Her's was a quiet, unseen, bottled up pitiful tiny mass of black energy. It would take much for it to become what he needed it to be, but that was alright.

He was a patient man, and after all, he had already made progress. It was reacting to the situation at hand, and that was all that he needed. She was but an apprentice, and he was a master, she did not yet have the skill or ability to detect what he was doing or defend herself from him. He found the lines of control she had over her heart, her darkness, and cracked them. Not destroyed, not broke, no, but simply cracked them. For the time being, that would be enough to allow her darkness to grow unhindered and weaken that controlled emotionless visage she usually bore. She would soon find herself slipping, and when that disciplined personality of hers found her control waning, he hungrily anticipated how it would eat away at her.

He pulled his mind out in time to see Eraqus scolding her. "That was uncalled for Aqua! I thought I taught you better than this. He brought Ventus here to be looked after by us, he made a mistake and admitted to it!"

Aqua bowed her head and banished her keyblade. "I... I'm sorry Master..."

Eraqus shook his head and pointed towards Xehanort. "I'm not the one you should be apologizing to."

Aqua turned and briefly bowed her head, mumbling, "My apologies."

There was distrust evident in her eyes as she looked at him. Yes, his little delve into her heart and emotional manipulation was working quiet well.

"You have nothing to apologize for," said Xehanort with fake guilt, "After all, I wouldn't trust me with him either, not after what my foolishness did to him."

Aqua narrowed her eyes, but said nothing. She did not trust the act he was playing. His eyes briefly flickered to Terra, to gauge his reaction. He was mildly surprised to see no anger, only a solemn nodding of the man's head. Oh right, that's why he had initially chosen the boy. He was far to trusting, easy to manipulate. Xehanort had readily admitted to harming the boy, put on a display of fake guilt, and Terra bought it easily. Now that he thought about it, it was almost off-putting how easy it would be to lead the boy astray. No, Xehenort wanted a challenge... he wanted to be worthy of the secrets of the Keyblade War...

When the darkness fell, he wanted to be worthy of the precious light the legends spoke of...

Of Kingdom Hearts.

He walked to the door, noting that Aqua had knelt down and moved to pick up Ventus. A thought, an idea struck him all the sudden. He had originally intended to just drop Ventus off and leave, but now, he had an excuse to return, to keep encouraging the tiny darkness in Aqua's heart to grow and blossom. Oh yes, this would work perfectly.

Xehanort turned briefly to look at Eraqus. "Before I go. Would you mind, old friend, if I returned now and then to check up on my old apprentice?"

Eraqus nodded. "Of course."

Xehanort did a double smile. One for the approval, and one for the stiffness that came over Aqua. He did another jab with his darkness, touching her paranoia and fueling it. She clutched Ventus protectively and stood, a warning gleam in her eye as she stared at Xehanort. He didn't answer that look, her merely turned and made for the door. As he heard Terra and Eraqus begin to leave, he decided to preform one last touch to really send her over the edge, he turned, and gave Aqua a cruel smile, sending another wave of paranoia and anxiety at her, making her clutch Ven even harder. With that, he left...

Aqua stood at the entrance to the inner keep, a shiver running down her spine. Even with that man gone, her anxiety still hadn't gone away. Something... something about that man seriously rubbed her wrong. And with good reason, she looked down at the unconscious boy in her arms sadly, just what had that man done to him?

"Aqua, let's get him to the guest room," called down Terra.

Aqua looked up and nodded. "Alright."

She walked up the steps and moved through the halls of the keep, holding Ventus protectively, looking at him with worry and concern. That empty look he had in his eyes, that cry of pain, to see him collapse like that, it hurt her to see it. Made her feel guilty for asking questions to cause the collapse. It hadn't been intentional, but it had still been her and Terra's fault. No...

It was HIS fault, that man's fault. Whatever he had done to the poor boy was the cause, and he was going to come back... why was he coming back?! Paranoia ate at her: She wouldn't let him hurt Ventus again... if he dared... she'd... she'd... make sure he never...

Aqua blinked a few times, feeling dizzy for a moment. She staggered a bit, her shoulder ramming into the wall. She winced and shook her head and looked down at Ventus to see if he was alright...

She let out a small gasp of fear and horror, sighting a weak glow of black and purple energy around her arms. It vanished a moment later, but... it... it had been from her, not from Ventus. That... that was darkness... why...?

She recognized the reason a second later. Her thoughts had been so hostile. She viciously shook her head, trying to clear her mind and resumed walking. This was what the Master so frequently lectured about. One had to maintain control of themselves, of their emotions, of their desires, and of their hearts, otherwise darkness could creep in like a virulent infestation. She took in a shaky breath and let it out, another shiver running down her spine and a jittery feeling entering her stomach. By the light, WHY couldn't she just calm down?

She walked into the guest room, sighting Terra preparing the bed, pulling back the covers to await Ventus. Aqua walked over, but hesitated... unwilling to put Ventus down.

"You okay Aqua?" asked Terra with a hint of concern.

"Just... worried about him," she mumbled.

She hesitated again, not really willing to let Ventus out of her arms, before she gave a heavy sigh and tenderly put the boy to bed and pulling the covers over him. She gently ruffled his hair and leaned forward to kiss his forehead.

"You... really care for him, don't you?" asked Terra, sounding a bit curious, "You just met him."

"He's so defenseless Terra," she murmured, "I... I'm scared for him, I have to care."

Terra chuckled softly. "Big sister Aqua, hah, well, it's not a bad thing."

They shared a quiet, awkward laugh before they grew quiet.

Terra frowned. "Aqua... I asked the Master when we went upstairs... that man, he was Master Xehanort, the Master's old friend. Why did you draw your keyblade on him?"

Wait, THAT was Master Xehanort? A mortified look crossed her face. She had drawn her blade on a keyblade master... oh man the Master was going to give her a lecture for that.

But...

Terra's question...

"I... I don't trust him, at all," she answered, her fists clenching, "He hurt this poor boy Terra, it's unforgivable."

Terra crossed his arms, giving her a stern look. "He seemed pretty guilty about it Aqua, everyone deserves forgiveness and a second chance if they seek it. Pretty sure both you and the Master lecture me enough on that kind of thing."

Aqua wanted to smile at that jab, but... her face fell. "I don't know Terra... I don't know..."

He gave her a concerned look before sighing. "Aqua..."

"I'll take first watch over Ventus," offered Aqua quickly, just wanting Terra to drop the subject.

Terra nodded slowly and left the room. "Okay. I'll check in with the Master."

Aqua nodded absentmindedly, pulling a chair up from the room's desk and sitting down. She ran a anxious hand through her hair, another shiver running down her spine. Why did she feel so shaken? It was... so hard to keep her feelings in check. From the moment she had heard that man, heard Master Xehanort admit to hurting Ventus, it was like she had been unable to regain control of herself... she didn't understand what she was feeling... what was happening to her?

"Am I... failing the Master's teachings?" she said, gazing down at her clenched hand fearfully.

There it was again, in response to her fear, a tiny black and purple glow around her hand. She shuddered and shook her hand, banishing it. She took in a deep and ragged breath, trying to force herself to calm down. She had not come this far in her lessons to fail at one 'little' slip up. She just... just needed a good nights rest. That's all... she'd put this all behind her, and when Ventus woke up, she'd help him recover and train as an honored apprentice of Master Eraqus. She'd keep him protected and safe...

And if Xehanort tried anything when he came to visit Ventus, then she'd...

She shivered again, her fists clenching, the faint dark aura appearing around her fingers again.

"Dammit," she whispered to herself, "Aqua, STOP it! You're better than this! If you keep drawing it out, it will only grow stronger!"

Why? Why was this happening to her all of the sudden? She had never had this issue before...

She leaned back in her chair and sighed, raising a hand to massage her forehead wearily. "My heart is of light, not of darkness... it's light... isn't it...?"

Terra back away from the half-open door, shocked and mortified by what he had seen. He had only stayed to peak and keep an eye on her because he had been a little concerned for her. But... that glow around her hands... that was darkness...

To see Aqua of all people struggling with it shook him to his core, left him rattled. She was so controlled all the time, he would never have questioned her ability to keep her own darkness in check. Was her control a front? To hear her questioning herself like that... how long had she been struggling with this? Days? Weeks? Months? Years? He couldn't get over it, she just always seemed to be in control of herself. He had never had a clue...

He had always thought he hadn't been applying himself enough to the Master's teachings, but he had never had what he had seen coat Aqua's hands ever appear for him. Was he actually doing better than she was? Was he more in tune with the light than her? Did he have more control over himself? Once the thought might have given him a bit of pride, now it only filled him with deep concern for his friend and a desire to increase his own studies and dedication tenfold as to not suffer the same self-doubt.

He walked quietly down the hall and made for the Master as quickly as he could, coming upon the man sitting on his throne in the audience hall, seeming to be lost in thought. "Master Eraqus..."

The man's eyes flickered to him. "How is the boy?"

Terra hesitated. "Still asleep."

Eraqus nodded before pausing, turning his head to study him. "Your troubled Terra. Do not worry, I'm certain young Ventus will..."

"It's not Ventus, it's Aqua," Terra answered quietly.

Eraqus frowned for a moment. "Yes, her... actions earlier were a bit out of character for her, I'll admit, but, everyone does have their off days. I'll talk with her about it, but, she has been a greatly dedicated student of the light, there is much you could learn from her..."

"Is there?" he questioned shakily.

Eraqus blinked a few times. "Terra? What's wrong?"

"Master... I think Aqua's having trouble controlling her darkness," confessed Terra.

Eraqus's eyes went wide. "What? Why would you say that of Aqua of all people?!"

Terra quietly confessed all that he had seen while watching Aqua, leaving Eraqus with an utterly lost look on his face. "Aqua... my dear student... I had no idea... Aqua, why haven't you come to me about this?"

"She never said anything to me either," said Terra worriedly, "Maybe... it was just an off day like you said, the darkness didn't seem to be heavy, just a minor..."

Eraqus shook his head. "Terra, listen to me. There is no such thing as 'minor' darkness. It's like an infection, it can only grow stronger and stronger unless you keep it tightly in check. You witnessed that anger from her earlier. If all it takes is one incident to make her lose control, then she is far worse off than you think, than either of us ever thought."

"What should we do Master?" asked Terra, "I don't know if confronting her about it is the best thing to do, but, I don't want to let it rest and just hope she'll get it under control."

Eraqus tilted his head in thought. "Hrm... I have faith in Aqua, for now, I will simply double down on her lessons as a 'punishment' for her actions against Xehanort. That way, she will not suspect that we know. If however she grows worse, if the extra guidance is not enough, I will take a more direct approach."

Terra nodded. "Okay."

"And for her sake Terra, I suggest you...," began Eraqus.

"Also double down on my lessons, I planned to," said Terra, "After what I saw... if that can happen to Aqua, it can happen to me to. I have to strengthen myself against the darkness."

Eraqus seemed surprised, and then greatly pleased by his words. "You show wisdin beyond your years Terra. I'm glad you've taken this as a lesson to use to strengthen yourself. Perhaps seeing you so dedicated will help her as well."

"I hope so Master," said Terra, "I hope so..."

Author's Notes:

Xehanort, you magnificent bastard. Manipulating and affecting Aqua, which in turn now leads to her questioning herself, in turn leading Terra and Eraqus to question her.

Oh how things are going to derail for our poor blue-haired heroine...