To make it easier on readers, I've chosen to break my 94-chaptered mammoth, The Undying Fire, into 5 books. Big thank you to dejavidetc for doing the amazing cover art for book 1!

Pohuai Stronghold was said to be impenetrable. The Yuyan Archers guarded its perimeter with hawk eyes and even quicker hands, ready to unleash a string of arrows that never missed their mark. Then there were the hundreds of warriors that patrolled the inside of the walls, all of whom had been handpicked for their dedication and skill. Zuko knew this. He'd known this every time he had snuck into the fortress, but he had learnt long ago how to become one with the shadows and move with the stealth of a panther-fox. Not even the Fire Nation's best could keep him out if he really wanted to get in, and in this case the dangers of being captured or killed were definitely worth the risk.

It had not taken him long to locate his target: the Avatar had been locked in one of the high-priority prisons, suspended by thick chains. Zuko had wasted no time in freeing him and dragging him off towards the exit, though he had been careful not to reveal his identity. It would be too much of a hassle to get out if the Avatar was resisting. Much easier to act like a friend or, at the very least, as if he really were enacting a rescue mission. Too bad the alarm had been triggered before they could escape.

"Stay close to me!" the Avatar called, running ahead and propelling a group of soldiers out of the way with a powerful wind blast.

Zuko frowned and quickened his pace. Seamlessly, they worked together, balancing steel with wind and raw strength with evasive grace as they fought side-by-side, never leaving a gap for the other to get hurt. Zuko would have laughed at the irony if his situation was not so desperate. Who would have thought that he and the Avatar would make such a good team?

Unfortunately, luck did not remain on their side. A desperate bid to make it over the last wall ended up in flames, literally, and then the two fugitives were surrounded once again. Zuko saw the four streams of fire coming towards them and realised with a grunt of frustration that he would have to break his cover to defend against the attack.

A hand grabbed him by the back of his shirt and spun him around just as a shield of wind came up to surround them both. That damned little monk had saved him again.

"Hold your fire!"

It was Admiral Zhao. Zuko turned his head sharply, fingers digging into the hilts of his blades as Admiral Zhao stopped in front of the line of firebenders.

"The Avatar must be captured alive!"

Without pausing to think, Zuko sprung forward and thrust his swords under the Avatar's neck, positioning the blades so that he could slit his throat in one quick swipe. For a moment no one dared move, shocked at this sudden turn of events. Zuko could feel the small body trembling against him, but he paid no heed to that and stared at Zhao through the slits of his mask, daring the older man to call his bluff, if it even was a bluff. Zuko wasn't really sure in that moment, half-distracted as he was by the adrenaline pumping through his veins. All he knew was that he was not about to surrender the Avatar just because they'd been cornered. He'd rather spend the next three years of his life searching for a new master of all elements.

Something in his posture must have tipped Zhao off, because he was suddenly giving the order for the gates to be opened.

"Admiral, what are you doing?" Colonel Shinu exclaimed.

"Let them out!" Zhao growled. "Now!"

Zuko heard the creaking jaws of something opening behind him. Very cautiously, he walked backwards with the Avatar through the gap, not once taking his eyes off Zhao. None of the soldiers made a move as the boys stepped out onto the path and continued to walk farther and farther out of reach.

Something wasn't right here. There was no way Zhao would let them go that easily.

"Look," the Avatar breathed. "The gate is closing."

Zuko said nothing and continued to lead him backwards, still holding the blades close to his throat. Zuko wasn't about to give up his advantage simply because they were outside the stronghold. He knew Zhao would still be watching. One wrong move and they'd be surrounded all over again, and he had by no means forgotten about the Yuyan Archers.

Frustrated at how long it was taking to get out of range, he threw a glance over his shoulder and was relieved to see they were almost at the crossroads. Just a little farther and they could make a break for the woods.

"Look out!"

Zuko turned his head just in time to see an arrow spiralling towards him. There was no time to duck, no time to defend.

Except the impact never came.

It only took a second for Zuko to realise that his broadswords had been pushed aside and that the small body pressed against his chest was leaning on him a lot more heavily than it had been two steps ago. Before he could process this, another arrow whirred towards them and he quickly rolled out of the way, pulling the Avatar with him. His heart pounded sickeningly when he saw the steal tip of the arrow bury itself into the ground just inches from his face. That had been too close.

"We need to get to the woods," the Avatar gasped, disentangling himself.

Zuko nodded and stood, sheathing his broadswords into the scabbard strapped to his back before he reached down and yanked the Avatar to his feet. Shouts could be heard from within Pohuai Stronghold and then the gates opened and figures in red burst through the gap like lava oozing from a volcano. Zuko's stomach twisted in dismay. Was this ever going to end?

"Hold on!" the Avatar yelled over the din. "I'll give us some cover!"

Dust and dirt gathered to form a cloud-like veil, blocking the two boys from the view of firebender and archer alike. Zuko had no time to be impressed. A hand latched around his wrist and pulled him forward, dragging him at an unnatural speed towards the woods. Only the slight breeze lifting his feet stopped him from falling flat on his face. He realised the Avatar must be using airbending to help him keep pace. It was an alarming and uncomfortably humbling discovery. He'd always prided himself on his independence and speed.

Branches snagged at the two as they crashed their way through the trees, though the barrier of wind protected them from taking too much damage. In the distance, Zuko could hear the yells of the men hunting them, but either Zhao's warriors took a wrong turn and got lost in the woods or the Avatar really was that fast, because soon the noises faded and all Zuko could hear was the rustling of leaves and the laboured gasps of his companion breathing.

Suddenly, the barrier of wind stuttered in front of them and Zuko stumbled to the ground. The Avatar pitched forward onto his knees, groaning and clutching a hand to his shoulder. Zuko's eyes widened when he saw the metal shaft sticking out from between the boy's fingers.

"No!" Zuko exclaimed, forgetting his rule to be silent. "Don't pull it!"

But it was too late. The Avatar wrenched the arrow free with a choked cry and rolled onto his back, legs curling up towards his chest as he whimpered in pain. Zuko slapped his hand away before the idiot could do any further damage. He crouched to examine the injury. Blood spurted from the wound in sticky globs, making it almost impossible to see anything. Zuko let out a small hiss of unease. Had the arrow pierced an artery?

Feverish grey eyes stared at him. "Is it bad?"

Zuko shook his head, not quite trusting himself to speak. With each drop of blood, he could see his visions of honour and home slipping away. He had no medical herbs on him, no bandages. Nothing but two swords and a mortally wounded Avatar who, Zuko thought in torn disgust, really was nothing more than a stupid child. A stupid child who had decided to throw himself in the way of an arrow that had never been meant for him.

Focus! a voice said in his mind, sounding a lot like his uncle. Don't let your feelings cloud your ability to think!

Zuko exhaled and closed his eyes. Right. Breathe in and out, in and out. Put aside fear. Put aside all emotion. Now come up with a solution to fix this mess.

His eyes snapped open and he clamped his hands down on the wound, trying to staunch the flow. Blood spilled through his fingers, warm and slippery, and not for the first time did he curse Aang for removing the arrow without first checking to see if it was safe. Just like a naïve, impulsive child. Didn't that kid ever think? Then again, he had been chasing frozen frogs.

Zuko's gaze drifted to the grey-tinged face. He couldn't help but notice how small and fragile the Avatar looked, like one of Azula's dolls before she incinerated it to ashes. It was an unnerving image, especially since Zuko was well aware of the power the Avatar could wield when pushed. Strange how one arrow could change so much. Of course, because of that same arrow, the Avatar's fate was now resting in his hands, as was Zuko's own chances of returning home. The spirits certainly had a twisted sense of humour. Not that Zuko found anything amusing about his current predicament. Blood continued to pump out of the open gash, no matter how much pressure he applied, and the Avatar appeared to be barely conscious.

Ignoring the steel fingers of panic that squeezed down on his mind, Zuko kept one hand pressed firmly on the wound and used his free hand to grasp the Avatar by the wrist, feeling for a pulse. A weak flutter greeted his blood-smeared fingertips. He paled as he realised he was running out of time. The Avatar was losing too much blood.

"Damn it!" Zuko growled, reapplying both hands to the wound. "Don't you dare die on me, Avatar!"

His only response was a flicker of grey eyes. Frustration and fear coiled its way through Zuko's veins, spreading through his body with paralysing venom. This could not be happening. That damned, idiot of an airbender could not be dying. Not now. Not like this. Not when he was so close.

"Snap out of it!" Zuko yelled, giving him a shake. "You're the Avatar, aren't you? So fight! Use your damn powers and save yourself!"

The Avatar's head lolled to the side, but there were no glowing arrows, no luminescent eyes. It seemed that even the all-powerful Avatar could not stop nature from taking its course. Zuko gritted his teeth. His heart pounded frantically in his chest as he pressed his palms harder against the wound, desperately trying to stop the blood from spilling out. If only the blood would go back in. If only he could seal up the artery and stitch the skin back together. It would all be alright then. It would all be okay.

"Come on," Zuko whispered, glaring as tears rolled down his cheeks, hidden by the cover of his mask.

So much of his hopes were resting on this child's life. So many dreams. If that heart stopped, if those lungs ceased to breathe. He could already envision what would happen. More years spent on a ship with a mutinying crew and an uncle who just wanted to drink tea all day and play Pai Sho. More ugly ice planes and frozen waters. More darkness. More searching—always searching—and never, never being able to return home.

"No." Zuko squeezed his eyes shut and shook his head. "I won't have it. I won't!"

He could still feel the warmth of the Avatar's life force pulsing into his palms. As he knelt there with his eyes closed, just willing the blood to go back to where it belonged, something stirred to life inside him—a fragile flicker of fire that seemed to spark from the very centre of his being. Like a tiny sun it burned, small at first, but then the flames began to expand as tendrils of heat spread throughout his body, filling him with a radiant energy. He realised that the fire was gathering in his hands, reaching out towards the source of that wounded, pulsing warmth. Trying to connect.

Fire is life.

The words sprang unbidden to his mind. Though he had no idea where he had heard the phrase, something just seemed to click. Exhaling deeply, Zuko focussed his attention on the bloody gash under his palms and felt a sharp tug on his gut. But no, it wasn't really his gut. More like something had reached into his very essence and was now pulling strands of fire from deep within him to form a bridge to the wound. He could feel pain and blood mixed in with airy whispers, but, more than that, he could feel the gaping chasm where chi should have flowed in the other boy's body, and which his own burning sun was now instinctively trying to fill.

Zuko's breathing sharpened as he struggled to make sense of what was happening. The sheer energy radiating through his veins was as exhilarating as it was terrifying, but it was also becoming increasingly painful. There was too much tugging, too much pulling. He felt like his soul was being ripped out from him, like his inner sun was being stripped bare of all its heat, leaving him empty and vulnerable and so terribly cold.

Panicking, Zuko tried to break the threads that linked him with the Avatar, but it was as if an invisible chain had lashed them together. By the time he finally managed to stop the connection, black dots were swarming before his eyes and he was conscious of a loud ringing in his ears.

When he tried to stand, Prince Zuko passed out cold.

oOo

Everything hurt. Aang groaned and opened his eyes, blinking a few times to gather his bearings. He seemed to be in some kind of clearing of trees and, judging by the pinkish tinge to the sky, it was just after dawn. Shaking his head to clear some of the dizziness, he sat up and saw a man in black sprawled out on the ground beside him. The grinning blue mask glinted wickedly at him. He gasped as memories flooded back into his mind: Zhao taking him prisoner, being chained in Pohuai Stronghold, the masked warrior coming to rescue him, the arrow, and then—

"My wound!" Aang exclaimed.

He shoved his blood-stained cape aside and examined the spot where the arrow had punctured skin. Streaks of dried blood covered most of the area, but though his shoulder throbbed and was tender to touch, there didn't appear to be any hole. Eyes widening, he quickly licked his finger and rubbed away the reddish-brown marks. A patch of rough, barely healed skin revealed itself, looking raw and shiny.

Shaken, Aang let his cape fall back to cover his shoulder and stared down at the masked figure near his feet. He couldn't remember everything that had happened last night, but the hazy images flickering in his mind told him enough to know that he owed the mysterious warrior his life. That still didn't explain how the man had known to rescue him or why he was now lying on the ground with all the appearance of one knocked unconscious.

"Hey," Aang said, poking the masked man in the ribs. "You alright under there?"

Masky, as Aang had decided to call him, didn't so much as flinch. Aang frowned and rested his chin on his hands. Maybe the guy was just sleeping. He was definitely breathing, except Aang still felt uneasy. Something weird had happened last night. There was no way an ugly arrow wound like that could just disappear, except somehow it had. Somehow, this mysterious man in the blue mask had healed him.

Aang stared through the hollow slits of the mask, trying to see past the darkness to the person beyond. Impulse made him reach out his hand towards the grinning face, but then he hesitated, chewing on his bottom lip as doubt gnawed at him. The monks had told him that one should always respect a person's privacy. This man was obviously wearing his mask for a reason. It would be wrong to breach that trust.

"Ah, one peek can't hurt," Aang decided, brushing aside his concerns. "I'll just make sure he's okay ..."

He gripped the cold wood and pulled—

And immediately regretted his decision.

"No," Aang breathed, stumbling backwards and dropping the mask with a clatter. "No, no, no!"

He felt sick. He felt angry, but more than that he felt confused. Because there was no mistaking that pale, angular face, nor the red scar that skewed the left half of the teenager's features. It was Zuko, the Prince of the Fire Nation, and the same guy who had been hunting Aang since he had first woken up in Katara's arms.

Shaking his head in denial, Aang leapt to his feet and made to bolt through the trees, but then he froze. Zuko might have chased him all over the world with the intent of capturing him, but Masky—Masky who was still Zuko at heart—had come to free him when Aang had thought no one else would. Masky had healed him.

Sighing, Aang turned around and walked back to where Zuko lay unconscious. He sat down on a nearby tree root and hugged his knees to his chest, occasionally throwing wary glances at Zuko. Maybe Sokka was right in calling Zuko an angry jerk with a ponytail, but Aang figured the least he could do was hear the older boy out. Perhaps Zuko had undergone a change of heart. Perhaps he was willing to help them now.

Perhaps ...

oOo

Something warm was touching Zuko's face, renewing him with heat and much-needed energy.

Sunlight, his mind supplied.

Yes, that was it. Sunlight. Zuko opened his eyes and was dazzled by the golden beams that streamed through the gaps in the trees. He winced and rubbed a hand over his face, pained by the intensity of the glare. Maybe he'd hit his head. That would explain the sharp throbbing at the base of his skull.

Groaning softly, he turned his face and saw a familiar boy perched on a tree root, hugging his knees to his chest. A frown creased Zuko's brow, but the Avatar did not glance his way.

"You know what the worst part of being born over a hundred years ago is," the Avatar commented, as if the two of them had been conversing the whole time. "I miss all the friends who I used to hang out with. Before the war started, I used to always visit my friend Kuzon. He was one of the best friends I ever had …" A glance towards Zuko. "And he was from the Fire Nation, like you."

Zuko said nothing. He didn't understand why he was being told this, but then a shy smile tugged at the corners of the Avatar's mouth.

"If we knew each other back then," the Avatar continued in a warm, hopeful kind of voice, "do you think we could have been friends, too?"

Grey eyes locked with gold, and it was as if a thousand unspoken words passed between them. Then the image of a man sitting on a throne surrounded by flames flickered in Zuko's mind, reminding him of his task. Reminding him of his destiny.

Zuko curled his hand into a fist. In an instant, he was back on his feet and a ball of flames burst from his fist. The Avatar dodged the attack and leapt up into the trees, jumping from branch to branch with all the speed and grace of a master airbender. Frowning, Zuko dropped his hand back to his side and watched the boy vanish from view, knowing it was futile to pursue him, knowing that he didn't really want to pursue him. Even his fireball had seemed weak, as if the anger needed to channel the attack just hadn't been there.

His jaw tightened and he glared at the space where he had last seen the Avatar, remembering that shy, stupid smile and the innocent offer of friendship that had come with it. Just like a naïve child.

Zuko turned his back on the trees. "We can never be friends, Avatar," he said flatly.

The Fire Lord had set him a mission. Zuko would not disappoint his father again.

Still, there was one thing that Zuko did not understand. He raised his bloodstained hands to his face and examined his palms, remembering the connection that had surged between himself and the boy. Remembering how the fire within him had reached out to the wound and then tried to fill that gaping chasm inside.

Zuko swallowed and his heart quickened in his chest. "Did I … did I really heal him?"

There was no one to give him an answer, yet the simple fact that the Avatar had managed to dance through the trees like a leaf on the wind suggested the boy had very much been healed. Zuko wondered if he could talk to his uncle about it, but then he realised Iroh would just ask him too many questions, and how was he supposed to explain that he had broken into Pohuai Stronghold to rescue—no, kidnap—the Avatar and then had somehow ended up healing the brat as well? He didn't even know that firebenders could heal. That was supposed to be a waterbending technique, and even then it was rare.

Zuko growled in frustration and threw his hands up in the air. "This is impossible!"

The whole situation made no sense. In fact, nothing about last night made sense. He would do better to put the matter from his mind. That was what his instructors would tell him: put aside all distractions and just focus on the task at hand. So what if the Avatar had spared his life by taking that arrow for him. So what if he had somehow managed to stop said Avatar from dying with spirits knew what kind of power. It had happened, and now he had to move on.

Zuko sighed and collected his mask from the ground, then headed back to his river boat to change out of his blood-stained clothes. Upon returning to the main vessel, he told his uncle that he was going to bed and was not to be disturbed.

It was a long time before he fell asleep.

Some things I want to make clear from the get-go. This is a "ripple effects" AU series that begins with the premise of Zuko discovering he is a fire healer through saving Aang's life. Changes to canon will be small at first, but will get more drastic until it's basically bye-bye to the canon timeline of events.

This series began as pure gen, but a very slowburn Zutara romance did creep in. (I give this warning because I know some people don't like this pairing.) That said, it's definitely more gen when all is said and done. In short, if you're expecting heavy romance, I'm afraid this series is not for you. If you enjoy friendship stories with plot and lots of character development, please keep reading.

Finally, I started writing this pre-LoK/comics, so for the most part you can assume what is established as canon in them is not relevant to this fic.