Title: Firelord Rising

Fandom: Merlin/ATLA crossover

Rating: T

Pairings/Characters: All Merlin characters with ATLA setting, Arwen, slight Mergana.

Spoilers: This story doesn't use either the Merlin or ATLA/LOK storyline, but you might recognize elements from both. I don't think there are any real spoilers for either show.

Warnings: Some intense bending action and angst.

Disclaimer: I do not own Merlin or ATLA.

AN: After a long time away from writing fanfiction, I have chosen to re-enter the life by writing a multi-chapter fic! Don't worry, I have a few of the chapters already written, so I will be posting while I continue to write the rest. My inspiration for this fic came while re-watching Avatar and Legend of Korra and realizing how perfectly and easily I could slip these two together, so I hope you enjoy! I would like to thank my dear friend, General San_3, for being my beta. She has helped this story become much better than it originally was.

Air. Water. Earth. Fire.

Five years ago, the four nations lived in fear of Firelord Uther and his anti-bending regime. But then, everything changed when the firebender Morgana overthrew his oppressive reign, killed him, and took his throne. Far from bringing peace to the world, Morgana proved herself to be a worse tyrant than Uther by conquering the Earth Kingdom using the power of Sozin's Comet, and now her eyes are turning towards the other two nations. Backed by a seemingly unstoppable army, where is the hope in defeating her?

In this time of war and land of fear, the destiny of four nations rests on the shoulders of two young men. Their names? Merlin and Arthur.

Some may have lost hope, but I believe they can save the world.

Chapter One: The Man in the Chimney

Chimney sweep had always been a lowly and unwanted job, even before the Fire Nation attacked. No one in Ba Sing Se wanted to climb the smelly, sooty chimneys and sweep and scrape and clean out the wretched ashes amid the fumes. It was a dark, menial job, one that earthbenders refused to lower themselves too, even though they could have gotten it done in about five seconds.

Arthur liked the job. It was menial, but menial meant that no one looked at him or cared about him. Menial meant safe. Even if it was something looked down on, even if his skin and hair turned dark like the ash, it made him fit in: blond hair wasn't a common sight in the Earth Kingdom, but within a few weeks no one gave him a second glance. Everyday, he woke up and ate a menial breakfast and went to his menial job and then returned home to his menial apartment.

He'd had a lot of pride and fight in him, back in the day. That was mostly gone.

All his needs were supplied by a tiny shop just a few streets from where he lived. He went there almost every day after work to buy food and other necessities.

One day, as he ducked out of the shop with his meagre supplies, Arthur spied a few Fire Nation soldiers coming down the lane, red flashing among the green and brown, pikes glinting fiery in the sun. His heart seemed to freeze for a second, and he quickly ducked into the blacksmith's right next door to the shop. When Arthur had first come to Ba Sing Se, he had been so careful not to stand out and be suspicious that he hadn't dared make sudden moves like that, but soon realized that everyone did that when soldiers came near; it wasn't a suspicious move at all.

The blacksmith, Elyan, was at the forge as usual, using metalbending to finish a sword. He did not spare Arthur much of a glance: coming into the shop and admiring the fine crafting was the only bit of unusual activity Arthur allowed himself, and he counted Elyan and his sister, Gwen, as two of his only friends. Both of the siblings helped with the smithing, but since Gwen had a better hand and eye for detail and not much mastery of metalbending, she supplemented their income by making clay pots. Arthur had sat by her one day as she bent the clay out of the container and molded it and shaped it and sent it into the kiln to fire. Compared to the quick, sharp, hard movements of most earthbenders, hers had been smooth and so gentle. He admired her a lot for that gentleness.

"You looking for Gwen?" Elyan asked curiously, leaning a little out of the smithy door. Arthur tore his eyes away from the earthenware-lined walls and shook his head.

"Um, no, just needed to get off the street for a moment," he said. The Fire Nation soldiers took that moment to march by, and Elyan's mouth thinned.

"Right," he nodded, understanding. "Don't want to get in their way." He turned back to his work and gave a particularly violent slice with his hand that nearly snapped the sword in half under the weight of his bending. "Those soldiers walk around this city like they own it! Like it doesn't rightly belong to us Earthpeople!"

Arthur was by the door, watching the soldiers as they turned a corner; only then did he relax. "They do own it, Elyan. They fought for it, and they won it."

"Hey, don't give me that talk, Arthur! You know all the Fire Nation is made up of nothing but thieves and liars!"

Arthur did not react to this statement.

"That Firelord sitting up there in her flaming throne is going to get what is coming to her someday, you mark my words. Us Earthpeople won't just sit by and wait forever. We'll rise up."

Gwen appeared in the back door of the smithy. "Elyan, are you having delusions of grandeur again?"

Elyan stuck his chin out at her. "Nah, this is real talk. I just know we're going to be free someday. I'll help with any uprising."

Gwen shook her head fondly, then went out into the shop to stand by Arthur, putting a hand on his arm. "Don't you listen to him, Arthur! We all know there's not a prayer of defeating the Firelord Morgana-not unless we have the Avatar on our side."

Arthur's mouth thinned a little more, but all he said was, "I had better be going," as if rousing himself from a deep sleep. "Thanks for the temporary retreat, Elyan. I'll see you tomorrow, Guinevere." He smiled down at her kind eyes. She blushed a little, just as she always did when he used her full name. He loved seeing that little blush.

The street outside was busy that time of day, as everyone was finishing their day of work and were heading home or buying supplies for dinner. Arthur did not give anyone a second glance as he strode through the masses towards his apartment.

Something prickled at the back of his neck, and he turned without thinking. Back over by the smithy, a Fire Nation soldier was standing very still amid the chaos of green- and brown-clad Earthpeople. He wore a helmet, but Arthur felt sure he was the one being watched. The soldier's companion was at one of the street stalls, buying vegetables. He seemed oblivious to his partner's intense interest.

For a moment, Arthur and the soldier locked eyes, then Arthur ducked his head and turned away, suppressing a shudder. There were any number of reasons why that soldier might have been looking at him, he tried to convince himself as he continued his walk. It did not have to be anything potentially dangerous. What troubled Arthur most was the glimpse of a patch he had seen on the soldier's right shoulder; patches could mean a few things in the Fire Nation army, but the most recent addition to that number, and the most likely, was a patch that Morgana had added. A patch given to firebenders.

He took the long way home, looking every which way so that he was not followed.

Gwen accosted him outside the shop on his way home the next day. "Arthur, I was hoping to find you today!" she said brightly, grinning. "We, uh, well, how has your day been?"

"Tiring, as always, but at least I had work," Arthur responded, feeling quite incapable of not smiling back as she slipped her arm through his. "You?"

She turned and started walking, so he followed her into the shop. "Quite good, I made a lot of new pots. I have a new design I've been working on, but it's experimental, so I shan't show you yet! It's always good to see you, Arthur, but Elyan did want to talk to you about cleaning the chimney again . . ."

The smithy's chimney was very dirty, as was to be expected, but Arthur had definitely seen worse in his five years of working as a sweep.

"I'll do the usual job," he said. "Put some salt on your fire tomorrow morning to clear some of the creosote away, and I'll come in the afternoon and scrap what's left. I don't expect it will take more than one visit."

Elyan shrugged. "Even if it did, wouldn't matter. A working forge is essential for a blacksmith, and I can't have the chimney dirty. Since the invasion, it's been really hard for business, and I think it's going to get worse for the next bit, what with all the extra soldiers that Firelord is flying in-"

Arthur's insides lurched. "What, extra soldiers?" he asked incredulously. Elyan nodded, looking stern but earnest.

"They've brought in a few more airships, just in the last day or two. I even heard she sent over a couple firebenders! I haven't seen one of those since the invasion! They're gearing up for something, I just don't know what. I wish I could show them what was what, but I've got my family here that I need to take care of, I can't just go rushing off to be a hero."

"No, of course not," Arthur agreed, not really listening.

Bringing reinforcements into Ba Sing Se? This hadn't happened in years. The occupying force had gradually gone down in the years since the invasion, and Arthur had not heard any rumors of rebellion recently. Why would Morgana be sending more soldiers in? What was her plan now? He thought about the soldier he had seen the day before. If he was right, and that had been a firebending patch, that man had probably come in with this new batch; firebenders were a rare sight anywhere outside the Fire Nation capital these days.

After talking through the last little details and agreeing on a price, Arthur set out for home, lugging his groceries again. He was lost in thought. He knew that if there were more Fire Nation soldiers running around, he would have to be extra careful; it wasn't likely that any of them would recognize him-he didn't think even Morgana would recognize him at this point-but he could take no chances. He could not go back to the Fire Nation and face everything that had happened there.

His mind churned as he walked the familiar path to his tiny apartment, and he felt as if he could not notice everything around him quickly enough. At this point, five years after his escape from the Fire Nation, the reinforcements probably were not here because he had been found, but Arthur hadn't survived this long by being negligent. He would have to be extra careful for the next couple weeks, just to be sure he had not been found.

Arthur lived at the back of a crowded and despondent neighborhood where other crushed and impoverished individuals lived. It was not the greatest environment, but the rent was about all he could afford with his menial salary. His neighbor Valiant was sitting outside on the veranda as Arthur came up, crooning to one of his enormous snakes. He made a sidelong cutting remark at the chimney sweep as Arthur inserted the key into the lock, but Arthur ignored him; he had dealt with too many unpleasant people like Valiant to feel any need to fight back.

Home was one room, with a tiny bed and a tinier desk littered with Arthur's meager possessions. The walls were very thin and the window wouldn't close properly, letting in a constant flow of dusty, smelly air. Arthur did not flinch as a couple roaches scuttled past his foot, but he did let out a sigh of resignation. He could remember a time when he would not have considered stepping into a room like this, let alone sleeping there, but, just like for everyone else in the world, everything had changed when Morgana attacked. Now his only thought was to keep himself safe and secure in this small existence he had. It was the only purpose he had left in life.

He sighed again, and began making dinner. It was not until he had sat down with his noodles and soup that he noticed something was off.

The window-that had never closed properly, ever, in all his time here-was completely shut. Arthur stared at it, dumbfounded. How had that happened? When he had left this morning, everything was normal; the chill morning mist was creeping in through an inch-wide crack between window and sill. What had changed?

Arthur stood and examined it. Everything seemed in order, but he could see no explanation for why his window was suddenly working again.

Unless . . . someone had been in his apartment while he was gone. Someone who had a managed to get it shut.

But who?

For a moment, Arthur's breathing came shallow and fast as he considered possibilities. Then, slowly, unhurriedly, he walked to the door and peeked out into the night. At first glance, everything seemed normal: little children screaming upstairs, clothes flapping on the drying line, stray dogs picking through the trash heaps-

-and two dark figures whispering to each other in the shadows. Secretive.

Arthur watched, hardly breathing. One was Valiant, he was sure of it; he would recognize that arrogant, snake-like posture anywhere. The other one . . .

Tall, maybe Arthur's height, but thin. Very thin. Arthur could not tell what the other man looked like in the shadows, but he could see a bit of his right arm and shoulder. He could see the patch sewn onto the black sleeve, the one with a black background and red flames.

Arthur silently closed the door and slid down to sit in front of it. He did not sleep that night.

The next morning was rough. One of his least-favorite customers needed to have a chimney swept, and he spent most of the morning scrunched into the tight space, listening as the owner critiqued everything he did. Arthur found himself wondering what would have happened if he hadn't learned to develop a thick skin here in the Earth Kingdom. Earthpeople did not really do subtlety; it was all up front and center, which was not what Arthur had grown up around. He managed to make it through the cleaning session having made only one smart comment, even if his eardrums felt a little overused. After sitting on the curb and downing his little lunch and water, squinting in the bright sun, Arthur set out to the blacksmith's. At least he would have one part of his day go right.

He should have knocked on wood.

As he reached just a couple streets away, he looked up and saw something that made his heart squeeze - the two Fire Nation soldiers he had seen from before were standing at the end of the street. The taller, broad-shouldered one looked up for a second as Arthur came into his line of sight, then continued with his animated conversation. Arthur could not run now; he would have to bluff it out. Walking like he was a simple chimney sweep without a care in the world, his wire sweep slung over his shoulder, he walked past the pair. The taller one kept talking, but out of the corner of his eye, Arthur could see the skinny one watching him.

Resisting the urge to either make a smart comment or run, Arthur turned at the corner and continued on to the smithy. He could feel eyes watching him all the way down.

He inspected Gwen's pots on the outside of the shop, trying to calm himself. I don't know what he's doing, but he can't have recognized you. He cannot have recognized you. You have changed so much you don't even recognize yourself. There is no way he could have-

"Hello," came a voice from behind him.

The soldier had removed his helmet, and Arthur could now see that he was a very young man, probably younger than Arthur himself, with dark hair and inquisitive blue eyes. He looked too skinny to be a soldier of any kind, except that Arthur knew he was the firebender he had seen the past two days. The other soldier was nowhere to be seen. Panic shot through him from his head to his toes. Almost five years of hiding, and he was going to be outed by a gawky boy?

He forced himself to stay calm and respond as a real Earth citizen might.

"What do you want, soldier?" he snapped, folding his arms.

The soldier blinked. "Come now, friend, I just have a couple questions to ask you."

"Do I know you?" Arthur asked, turning his back again.

"No," the young man replied, laughing a little. "We've never met, I'm sure. "

"And yet you call me your friend," Arthur said stiffly, looking at the other man. The young man shrugged, looking a little uncomfortable, but smiling again..

"Just trying to diffuse the tension," he replied. "I just, uh, well, I used to live in the Fire Nation, you know! And I thought you looked a bit like someone I-"

"Are you saying I look like someone from the Fire Nation?" Arthur said in a dangerous voice. "Because I wouldn't like to think you were saying that. You may think you own this country, firebender, but this is our turf." He scoffed and turned away. "Saying I'm like you . . . As if you could insult me or my country any more." His heart was pounding fiercely, because what if he had been recognized? What if this skinny young man did know who he really was? The glint in his eye, the quiet watching, the conversation with Valiant, all certainly suggested that.

The firebender's eyes narrowed, and he looked about to give a heated retort, but Elyan stuck his head out of the smithy door.

"Hey, Arthur! This man bothering you?" He gave the Fire Nation soldier a look of hearty dislike.

Arthur could have hit him, because the soldier had a look that said Elyan had just told him everything he needed to know; it was times like this that Arthur wished he had had the forethought to use a fake name when he first escaped to the Earth Kingdom.

He took a deep breath to calm himself, and smiled tightly. "No, Elyan, we're fine. Listen, I'll have to come back later, but I'll finish cleaning that chimney for you."

He turned back to the Fire Nation soldier, who was watching the exchange with his eyebrows pulled together. "You're a chimney sweep?" the young man said, looking confused.

Arthur put his hand firmly on his shoulder. "Why don't we go for a little walk, and maybe afterwards you'll understand about life here a little better, eh?" He started to lead the firebender down the street, his heart sinking lower with every step he took. Elyan was watching him go with a worried expression, which was just as well; Arthur knew what he had to do to keep his secret.

He would have to kill the firebender.