1 Chaos Theory

It was beginning to look as though there were nothing at all of interest in the entire expanse of this desolate future world. After stumbling out of the gate leading to Noel's dream world, hoping to find Valhalla or at least someplace with some greenery, they had only found more of the same. Serah was beginning to think they would never find a way to Lightning at all.

"Let's keep poking around," Noel said. "Usually the gates are pretty close together. We shouldn't have to go far to find one."

Serah wasn't so sure. "Maybe. But– wait, what's that?"

Some distance away in the middle of the village, a slender golden pillar of light had appeared out of thin air. The two travelers exchanged glances before advancing toward it. There was no telling what might come out – more rift monsters, or even their adversary, or something even more horrible. They stuck close together as they walked with their hands ready to reach for their weapons.

There wasn't any wind. Everything was so cold and dry that there was nothing to block it even if there had been any. The sun was long gone, leaving a faint touch of bronze in the sky. The stars were coming out and all was peaceful with absolutely no other noise besides their breathing. The only source of light beyond the stars and the fading light was the golden distortion before them – one that flared bright and threatened to ignite the air before a slender human shape walked out of it.

The air may have been cold, but in that moment, Serah felt as though a brilliant new sun had risen to heat the world and bring back life.

It was her sister. Her dear sister, just as she had looked in the images of the Oracle Drives they had come across in their journey, walking out of the golden distortion with the dignified steps she had come to expect from a woman who had spent most of her life at war. Except for her downcast expression and lowered chin and strange Valkyrian armor, this meeting was no different than any of their others.

"Lightning?" Serah almost gasped the word. "What– you're here."

The woman looked up, something unreadable in her blue eyes – was that despair? Sadness? Even grief? "This is a future I couldn't save," she murmured.

But Serah didn't care about that. "You're here. You're here. I mean– we came all this– how did– is it really–?"

"You doubt me?"

Serah hesitated. "Well…"

"No, no," Lightning interrupted, smiling and shaking her head. "That you doubt anything… I'm glad. After all that's happened, it's good to doubt. You're growing up."

Serah brightened. "It is you, isn't it?" She stared at her sister a bit longer. They had come across space and time in a long journey to find this woman as she'd been told, and from her perspective it had been three years since the two sisters had seen each other last. Three years, during which most people, except Snow, thought she was crazy for believing Lightning was even still alive with no evidence to prove that belief.

She spent a second fighting her childlike urge before bounding forward and throwing her arms around Lightning's torso, strange silver armor and fluffy white feathers and all. Noel gave a grunt of surprise while Lightning stumbled before returning the hug. Serah felt warm all over, better than she had in way too long.

Lightning chuckled. "I'm glad to see you too, Serah."

The other woman hung on a moment longer before prying herself away. There would be time enough for that later, when everything was all over and everyone was safe – time enough for reunions and happy moments once all the important things were taken care of.

"And Noel – you've been doing very well, taking care of her." Lightning nodded to the darkhaired boy, who looked embarrassed.

Serah could barely contain both her excitement and her million questions. Before another five seconds had passed, they tumbled out like a busted levy. "Where have you been? In Valhalla, all this time? What about Cocoon and saving the future? I've been looking all over for you! Did you really disappear? Did you–"

"Serah," Lightning said, and gently touched her shoulder. There was something in her eyes that spoke volumes in a way her voice just didn't. "Just listen. I can explain everything."

"Really, everything?" Noel put in.

"From Valhalla, I can see the entire timeline," Lightning said. "Now that we are together again, I can tell you how we came to this terrible fate, and about the one who wants to destroy the future."

Noel growled softly. "Caius."

Lightning walked past them now, crunching across dead twigs and rattling stones underfoot, the click of her armor and the rustle of the feathers the only other sound now. Serah listened to the sounds as they all came together in an alien symphony she couldn't quite catch the entire rhythm of. Lightning walked until she reached the rickety foot of the steps leading up to the old Bodhum pier, half of which had snapped off long ago. What remained stretched over a badly-eroded seafloor void of water with the remains of sea creatures littering the bottom. She stepped up onto it, where it creaked in pain.

The two travelers listened as Lightning explained everything that had happened so far – about how chaos had come into the world and dragged Lightning away as Etro had reversed the damage she'd accidentally caused by freeing her and the others from their l'Cie fate; how Lightning had tumbled through the Historia Crux and watched time become a surreal freefall of paradoxes and bizarre twists of fate; how she had been written out of history in the meantime; how she had ended up in Valhalla and taken up the mantle of being Etro protector; how she had seen the sad future of mankind and resolved to prevent it.

"It would be my atonement for everything I had ever done," she finished, facing them now. "Caius wants to destroy the future and all hope. We cannot fail if the world is to go on."

There were a few moments of silence.

"So," Noel murmured, "chaos came into our world, warped the timeline, and formed the paradoxes. Makes sense."

"Lightning," Serah was almost afraid to ask, "the future of mankind… what'd you see?"

The woman frowned slightly. "I'm not sure," she admitted quietly. "Something terrible, something I hope we never have to witness. The world falling into the void. The end of time. Caius charges endlessly at the temple in Valhalla while Etro holds chaos back from entering our world, and he seeks only a blind desire to kill her."

"And if that happens…?" Noel coaxed.

"Chaos would gush into our world and cease the flow of time, collapsing the past, present, and future. The world would become true entropy – no life, no death, no time."

"Like Valhalla." Serah chewed her lip. "That's what he's after, isn't it? If he can erase time–"

"Yeul would be saved." Noel seemed in awe of this, if briefly. "And not just one. All of them. The ripple effects would travel up and down the timeline and free every one of them from their curse. They'd be safe and never have to die or be reborn or see the future ever again!"

"Exactly," Lightning said. "The ripple effects would keep them alive."

Another pause. Noel seemed to be thinking.

"How would he do it?" Serah asked.

Lightning pursed her lips for a moment. "The gate must open very wide if enough people die at once, and when that happens, chaos would gush out into the world. For example, if Cocoon should fall," she added, looking between the two. Apparently making sure they were both listening, she frowned at Noel, causing Serah to look, too. The boy stared blankly into the distance. Lightning kept talking. "Caius must be stopped on both fronts – here, and where I come from. In 500 AF, he'll make his final move, and at the same time, he will come after Etro in Valhalla. I must go back to stand in his way. Can you try and prevent Cocoon from falling?"

"We can," Serah answered, glancing at Noel again. No change.

"I know I can't count on you. Mog will show the way."

Serah watched the little creature go flying off to reveal a gate at the end of the rickety platform, then looked back at Noel and nudged him. "Hey. You alive?"

"Hmm?" He blinked at her. "I'm… thinking. But I got it."

Serah said, hesitantly, "What?"

"I'm just– I'm wonderin'." Silence. The three travelers looked between one another. Noel squirmed, sighed, and rubbed the back of his neck. "Thinking. You know how Yeul is constantly reborn? I'm just wondering– you know, just a thought, but… is it involuntary?"

Serah and Lightning exchanged glances; the latter looked surprised by this thought. "What do you mean?" she said.

"Haven't you looked through time at all to the distant past?"

Pause. "Not all that often."

"Well, you knew Caius had been a l'Cie before. Did you see anything to indicate whether Yeul chose come back, again and again, or whether it was really a curse and she just can't help it? I don't know," he muttered, frowning and shaking his head slightly. "Can't tell what to believe."

"But even if she did," Serah put it, "that wouldn't matter. Things would still go the way they–"

"No. Wait." Lightning stepped down onto the beach again and looked at Noel. "I see what you're saying. If Yeul chooses to come back…"

"Then it's kind of her fault this happened," Noel finished, "so if you can somehow tell her to stop coming back, maybe back when this all started – tell her what's gonna happen, and how everything'll fall apart… maybe even get her to tell Caius if he doesn't already know, which I suspect he doesn't–"

"The timeline only goes back so far, Noel," she sighed, "and at this point I'm not sure what difference it'd make."

"But it's worth trying, right?"

Her blue eyes narrowed momentarily before she nodded. "Yes. I suppose anything is at this point."

Serah nodded as well. "Worst comes to worst, we'll help out anyway we can."

There was a severe, determined look in Lightning's eyes, one Serah had seen a few times before. The lines of her body were taut with her shoulders firmly back. There was no doubt about it: now that Lightning had a goal other than just fighting to save the world, things seemed to be a little clearer to her. The three looked at each other again before Lightning nodded once more.

As she headed past Serah back toward the portal, Serah said, "Lightning?"

The woman paused and gave an acknowledging hum.

"We'll be together again, right? Once all this is over and everything's back in one piece again?"

She heard, rather than saw, the slight smile on Lightning's face. "One thing at a time, Serah," she said, and moved off again. "One thing at a time."

Serah stared at the ground between her feet as she heard her sister's footsteps vanish at her back.

Caius slipped on the stone underfoot and again wondered why he was clawing his way up the side of the temple instead of just flying up. True, he might need the exercise after sulking around the northern half of Valhalla most of the week, but that wasn't much of an excuse. Then again, he was less likely to get caught until it was almost too late if he climbed, especially on the side closest to downtown. What handholds he found were pretty secure even given their age; he could climb fairly swiftly as long as he didn't look down. Immortal or not, hitting the ground spine-first and shattering it wasn't a pleasant experience.

Two-thirds of the way up, he paused, held his breath, and listened. Other than the muted roar of the ocean, he didn't hear anything.

Smirking to himself, he continued up.

Darkness had settled over Valhalla by the time he hauled himself over the rail and onto the balcony. One hand on the rail, he listened again. Except for a vine rustling in the breeze beside him, he didn't hear anything at all, not even his adversary pacing back and forth on patrol. That seemed rather odd, but he didn't question it. He moved away from the balcony, slinking along the wall and sticking to the shadows of the throne room. The top half of the temple had been blasted away by his attack on it earlier, exposing the throne to the elements. Most of the pillars had been snapped in half as well. He was completely exposed even with his back to a pillar in the corner.

Still no sign of Lightning; he couldn't believe his good fortune.

The nagging question of where is she lingered in the back of his mind, though, so he waited a second longer.

Still nothing; he moved forward.

"I was wondering how long you'd hold out, Ballad."

Hesitating, he lifted an eyebrow. So much for his good fortune. "Lightning," he said by way of greeting.

He heard the sound of her armor clicking together, metal ringing on metal, before he saw her come out from behind a pillar on the far side of the throne room. In her right hand she bore her long silver gunblade, held angled down in a resting position, but he knew how fast she could reverse that. With her head up, walking with graceful steps even in the cumbersome armor, he could almost say she was elegant.

One hand grasped the handle of his sword. "I was so close," he said flatly. "Closer than I have ever been."

"Sorry to disappoint you," she muttered.

The massive sword came off his back to point at her. "Then we should end this."

Her sword mimicked his. "You say that a lot. Is fighting the only way you know to end a war?"

"In this case… yes."

There was something in her clear blue eyes that had never been there before. It made him curious. "Just let me ask you one thing," she said, and looked him in the eye. "Why is it that you set out on this journey and sought to bring about the end of the world?"

Bitterness enveloped him in a red haze. "Because Yeul always dies far too young."

"Is that it?" she said. "There's no desire of yours to be free of your own curse?"

"Of course there is!"

"And Yeul, returning again and again…" Lightning stepped forward. "What if it's a choice?"

This promptly sent him off the deep end. How could anyone even suggest that? How could she say such a thing? "A choice? A choice! Lightning, you ignorant fool, who would choose to die young only to return and suffer the same painful fate over and over? It never ends! So I will end it for her!"

Leaping straight at Lightning, he seemed to catch her off guard for the briefest of seconds, which was all the time he needed. Together, in a tangle of arms and legs, they went flying back toward the far balcony, skidding on the stone when they landed. He twisted, trying to stand, but he felt her latch onto his throat and begin to squeeze, choking him. Coughing, he and returned the favor, only to feel her slash down his side, leaving a scar on his armor. A second later, she punched him in the stomach – hard enough that the armor couldn't swallow the whole impact of it – and as he struggled to breathe, she rolled away and stood.

Then she pounced and knocked them both off the balcony.

They hit a lower building together, him landing shoulder-first and taking the brunt of the impact, teeth cracking together and giving him a headache; she rolled with him and used the momentum to launch herself up onto her feet a smart distance away. He flipped over to stand as well, not wasting a second before sending out a burst of energy that made her stumble backward.

He pressed the offensive, forcing her back. She finally gained some footing and reacted by turning her sword to catch his between the main blade and the bayonet above it, locking them together. With a flick of the wrist, she yanked him to a stop. He grunted; she glared at him. This went on for a second or two before his vision suddenly went white and he landed on his back on the street.

Confused, he blinked, trying to clear his vision, seeing her falling toward him. Before he could bring his sword up to try and catch her on it, she landed beside him.

In a sight panic, he rolled aside and scrambled to his feet. They were in an alleyway, a rather tight space to keep going in such a war; he looked all around while keeping an eye on her at the same time, searching for some way out of this mess. Lightning advanced on him; he backed up, still looking for a way out. Then, suddenly, he reversed that tactic and leapt straight at her again; she reacted by imitating him. Crack went galvanized armor on coated metal, an impact that made his head spin – not an unfamiliar feeling. Before he could do anything else, she ducked his blind swing and kicked him, hard, in the face. He went tumbling out of the alleyway.

Once more, she was on him, but this time he forewent the defensive and struggled away from her. Quickly scaling a building with strangely gnarled architecture, he scrambled across the rooftop, aware she was practically breathing down his neck, leapt to a neighboring one, and, in midair, twisted to fire a nice blast of fiery energy that engulfed her and sent her tumbling to the rooftop in a daze.

As she somehow managed to stand, he threw out a beam of purple light that knocked her over. A second later, with shaky steps and terrible balance, she managed to stand. Caius hid his frustration.

"Will you never give up?"

Her blue eyes narrowed. "You'll never see me quit."

"Even if time ceases to exist and all of time collapses? Even if all potential and possibilities collapse?" He scoffed at her, taking a step toward her with his sword up. "Pointless."

"You'll have to kill me first!"

Caius smirked dryly at her and snapped a hand forward. A graviton burst sent her flying back into an open plaza one level above the beach; he hurried after her, knowing he had to keep pushing or else he would lose what advantage he had at the moment. As long as Lightning still breathed, he wouldn't be able to finish the job; he could only hope one of his past selves would instead.

As he landed hard on the stone and stood, she already was, shield up in a guard position, sword angled to block any strike he might try.

"And you think this will make Yeul happy?" she demanded.

Caius faltered a second. "At least you know I'm not doing this because I can."

She dodged a beam of energy that raced along the ground by leaping aside. When he sent a second beam after her, she dodged that one too and deflected a follow-up pearl of light. "You want to save her, but in doing so you want to wreck the lives of everyone else?"

"Imagine watching your dear sister die over and over for centuries, unable to control it, helpless to stop it!" he shouted, and ran at her. They came together in a very loud crack of sword and sword that made his head hurt, but he managed to unhook his from hers and take a swing.

"Haven't you ever stopped to think that maybe, just maybe, she chooses to keep coming back? That she chooses to keep suffering?"

"No!" He turned his fury into a flurry of strikes that forced her back, finally catching her blade on his and using his weight to push her back even further. "How can you even say that? She–"

"Because she told me!" Lightning dug in, slid to a stop, and pushed back. The two of them pushed against each other with both physical strength and sheer mass, although Caius, the heavier of the two, had the slightest upper hand in that respect. "You know I spoke to her? Personally! I reached back through time and finally wrenched the truth out of her!"

"What truth?" he shouted. "What didn't she tell me?"

"She wanted to tell you, but she couldn't!" Lightning dug in a little more, finally able to use leverage to force them to a momentary stalemate. "By the time she thought it might be a good idea to mention that she'd chosen to come back time and again, she couldn't do it!"

He laughed bitterly. As if he could ever believe it! "And why would she keep coming back, hmm?"

"Because you were an immortal and she was the only one who could! She came back to be with you! To keep seeing you! So you wouldn't be lonely!"

Lonely? Caius couldn't think of a time when that hadn't been so. Just the knowledge that his time with each of the girls would be hideously short was enough to keep it that way. No matter how many years he spent watching her grow from an infant to a teen that would suddenly, without warning, die in his arms, it never changed a thing. He had always been lonely. That was his curse.

"She wanted to keep you sane, keep your feet on the ground and your loneliness at bay. But it backfired." Lightning was still talking, staring at him through crossed blades. "Oh, it backfired! Instead of enjoying what time you had together, it got worse!"

Panting under the strain, he gritted his teeth before speaking. "And what of it?" he demanded. "So Yeul chooses to come back. So what? It makes no difference! Too much has been lost!" Giving a hard shove, he made her stumble back, then kicked her sword into the air before striking her across the chest with the flat of his. She coughed and fell to the side, landing on one knee. "I will save her!"

Lightning coughed, one hand held against her belly. "You're so hardheaded," she muttered. "She came back over and over to be with you, wanting to come back, but when I asked her why she did it even now, once she knew what was to come, she said she just couldn't stop anymore because you'd just go on and finish your plan anyway, since all those girls in the past had died." As she spoke, she climbed to her feet and dodged a swing from his blade, which made him bristle. "Don't you see? It's all a lie, Caius!"

"I won't stop!" he snapped.

"Fine!" Lightning brandished her sword, and they clashed once more, swords flashing in the strange bluish ambient light of this otherworld. "Fine, Ballad! Then think about this. What about making it so she doesn't have to come and keep you company? What about a companion?"

This was the most absurd thing she'd ever said to him. Had she spoken without thinking, or did she honestly believe he'd never considered it? "I'd outlive anyone!"

Lightning looked exasperated. "What about the Heart of Chaos?"

"What of it?"

The sound of crashing blades filled the gaps between sentences as they continued their dance into the deepening night. "You can control it! It belongs to you! I know you can't hand it off completely without killing yourself, but maybe you can split it! Give half to someone else!"

He sneered at her. "What?"

"Let her go! Pick someone else, someone who will stay through thick and thin! Fine someone! Let her move on and die in peace!"

This was something he had considered and discovered to be possible, but it was still absurd. "And give it to who, warrior?" he demanded. A graviton burst sent her skidding back across the plaza. He charged at her; she narrowly blocked his strikes. "No one will take it willingly!" Crack – he missed and hit the stone; Lightning pushed off it and landed on her feet. Caius came after her with each strike punctuating his words. "No one will stay with me! I will never have anyone because who would do it? Who would willingly bear my curse at my side? Who would take pity on a monster and stay with me? No one! Do you hear me?" Practically screaming now, flooded with adrenaline, he swung the blade and sent out a shot of purple energy tinged with pink. She blocked it with her sword, but still she backpedaled and tried to stay upright. As she fell to knees, barely keeping her legs beneath her, he swung down and brought the blade crashing against her sword. "No one ever would!"

Lightning shouted the most terrifying and unbelievable words he had ever heard out into Valhalla's alien dusk.

"I'll stay with you!"

And for the first time since they had started this war, everything fell deathly silent.