The Avatar was a very hardworking man.
After defeating the Fire Lord, Aang had forgone the honors bestowed upon him, and begun to help rebuild the Earth Kingdom and Water Tribes by hand rather than through political support. There was always a village to rebuild or a forest to replant, and for the first four years after the war Aang spent most of the time assisting those efforts in any way he could.
When he wasn't rebuilding other cultures, he was up in the air temples rebuilding his own. He spent most of his free time at the Southern Air Temple with his wife, Katara, repainting murals and repairing derelict old walls with new, stronger materials. There wasn't a task that he wouldn't do, and though it meant spending most of his time away from home or staying awake for days, Aang took pride in his work and worked tirelessly to do his part.
While Katara understood, she didn't like how long Aang spent travelling. She had gone with him to the North and South Poles, but recently Aang had been travelling alone to the far reaches of the Earth Kingdom. She didn't mind so much, it's not like she spent all her time cooped up in the Southern Air Temple - she travelled when she needed to, and she still played a part in Water Tribe and nearby Earth Kingdom conflicts. But whenever Aang came home, he'd always look so tired and go straight back to working on the air temple. Whenever she suggested that he take some time to relax, he'd look at her and say the same thing in the same lackadaisical tone of voice.
"I'm alright - this is what I want to do."
As much as she loved him, the situation was beginning to make Katara anxious. She knew him as well as ever, he wasn't changing radically every time he came home - except when he brought back new clothes and stories and ancient customs from the Earth Kingdom, in which case he was a bit full-on to be around for a few days afterwards - and while she could respect his space, she couldn't help but worry about how hard he was pushing himself and how little time they spent together. She wanted time with her husband, she wanted to see him well-rested and contented. Just once, she wanted to see him relax and take a load off like when they were children, to remember that there was time to relax even under the toughest pressure.
But she persevered, for his sake - like Aang did for her and for the world.
It was late in the afternoon, where the color of the sky subtly shifts into the rich red and gold expanse of twilight, that Katara first received news of Aang's illness.
He had been tearing down ruined huts with a wrecking crew when his strength had failed him, and he had gotten trapped under some light rubble. Even after being moved into a clear and open area, with little physical injury, he struggled to breathe and couldn't support himself. The doctor tending to him had diagnosed him with fatigue, and had sent a message by hawk requesting Katara's presence. For the first time in what felt like ages, Katara left the Southern Air Temple to be by Aang's side.
When she got there, Aang seemed fine. He was as lively as ever, telling her about the village they were in and about the other villages along the way, local stories, traditions and the like. But something stood out - he wasn't walking around and helping. He was relegated to bed rest - it was the first time in ages that Katara had seen him lie still.
According to the doctor, Aang's strength had slowly diminished while he was in the village, and it hadn't been returning. While Aang insisted he was fine, the doctor said otherwise - he had called Katara to take him home for a month of rest. Although he protested to begin with, Aang eventually complied and he and Katara made the journey home.
The month of bed rest was like a fresh start for the pair. For the first time in years, Aang had the time to sit down and enjoy the scenery, and with Katara by his side he felt an overwhelming urge to rest and get better for her sake. He slept for days sometimes, making up for years of unyielding work and sleepless nights, and when he was awake he focused his attention on Katara. He picked wild flowers from the most obscure nooks and crannies of the temple, he prepared dinner when he wasn't relegated to bed rest, and when they were together he made an effort to be close to Katara and to hold her in his arms whenever he could.
It was during this month that they conceived their first child, though Katara wouldn't realize until Aang left again.
It was after a three month trip that Aang came home afterwards, and the news shocked him to his core - the idea delighted him and terrified him all at once. Needless to say, after hearing the news, Aang was home a lot more than usual. He made an effort to balance work and rest, as a responsibility to his family - his travels began to shorten from months to weeks, and whenever possible, even days.
Rather than take a physical role in rebuilding the world, he became more of a consultant to the surrounding areas. It was during Katara's pregnancy that Aang began the Air Acolyte program, giving people the opportunity to learn the customs and lifestyle of the Airbenders as well as to help restore the air temples. The program did involve travelling, but he made sure to be home every two weeks at the latest.
It was during a visit to Ba Sing Se that Aang collapsed a second time. He hadn't been pushing himself too hard, mostly missing a bit of sleep and holding long meetings to discuss the Acolyte program with dignitaries and investors. He had collapsed after a particularly long workshop, and was tended to by the best doctors and healers in Ba Sing Se. For the second time that year, Katara made the trip to see her sick husband.
This time, the diagnosis wasn't so light.
Ba Sing Se's best healers had detected a block in Aang's chi. Something had grown in his body and it was interrupting his blood flow and bending ability, and they had concluded that it was blocking Aang's energy from being properly distributed. The head healer had described the block as like a leech, feeding on him from the inside of his body. Given Katara's experience with healing the Avatar after nearly dying in the fight for Ba Sing Se, they requested her opinion - and when she began the healing process on Aang, she clearly felt the blockage they had described around his liver.
This time, they requested Aang return to the Southern Air Temple indefinitely and spend three hours a day performing circulatory bending techniques. Hopefully, according to them, it would clear his chakras and improve his health. With his planned tour now cancelled, Aang returned to the Southern Air Temple - but even without his help, the Air Acolyte program flourished. The program received a boost from Ba Sing Se's cultural board, and with correspondance from Aang they worked out the terms of the program. It was initialized, and the response was great - in time, benders and non-benders alike came to the air temple to learn from Aang.
Months passed, and then years. Katara gave birth to a healthy baby boy, and Aang kept busy by guiding the Air Acolytes though life as an air monk. He didn't travel any more - while the three hours of circulatory bending kept him healthy and in a good state of mind, it was clear that the blockages that he'd been diagnosed with were growing and spreading. At the age of 25, it seemed clearer with each passing day that Aang would not be around for much longer.
The only people who knew how bad his condition was getting were Katara and Aang. Their son, Tenzin, was undergoing training with Aang's guidance - Aang argued that it was more important for Tenzin to focus on his culture in a good state of mind than to learn with the pressure of being the last Airbender, a move Katara disagreed with given that Tenzin would be the last Airbender anyway, and should know as soon as possible that his father was dying - but training came first to Aang, and he worked as hard as he could to pass his knowledge on in the time he had left. In a way, his actions seemed frantic - like he felt a responsibility to keep his culture alive against his own wishes for his son.
It was late in his illness, as they were walking back to the living areas from a meditation session, that Aang broke the news to Tenzin. He was upset, of course - he knew about the fate of the Airbenders, and the thought of losing his father as well as the only other Airbender in existence was a horrible burden to receive. Tears were shed from both Tenzin and Aang on the way home - but by the time they returned, both of them had come to terms somewhat with the situation and gained a solid sense of respect for each other, as individual people and as father and son. It was later that night, as a mark of respect and a symbol of Tenzin becoming a man, that Aang began to work on Tenzin's arrow tattoos.
As his condition worsened, Katara began to miss Aang's long trips. As lonely as it was, he was out in the world doing good things and being active. He would always come home and have energy to expend, enough to go straight back to repairing the air temple even through his visible weariness - seeing him get slower and more decrepit was immeasurably heartbreaking. It had progressed to a point where Aang couldn't walk without his staff, and it was becoming clear to the Acolytes that Aang was a very sick man. All Katara could do was send out a swath of invitations, to everyone from doctors to their own friends and family, to let the news become known and to give everyone the chance to say goodbye.
Aang's last act as the officially recognized head of the Air Acolytes and cultural expert on the Airbenders was to complete Tenzin's tattoos. At 9 years of age, Tenzin was the youngest Airbender in history to gain his tattoos, and the first Airbender in over a century to gain the markings. The ceremony was documented by Tenzin's uncle, Sokka - a respected map-maker, and a growing diplomat - and everyone who stood by Aang's side during the war against the Fire Nation was in attendance, from one of the most revolutionary Earthbenders in history to the revered leader of the Kyoshi Warriors, to the Fire Lord himself. Zuko's presence officially marked the first welcome Fire Nation visit to Air Nomad soil in over a century, and he declared an official apology for the Fire Nation's actions towards the Air Nomads as the event drew to a close. News of the apology spread around the world, and in the years afterwards it was acknowledged as a historically significant step towards world peace.
It was only three days later that Aang lost the strength in his legs, and was rendered bedridden. Trying to soothe Aang with an intensive water-healing session, Katara couldn't help but gasp in horror - the blockages were everywhere. They were in his abdomen, chest, legs... it felt like they were more of them than there was of Aang. There wasn't enough blood circulating to keep Aang healthy, and if he had the energy to bend, she imagined he wouldn't be able to muster more than a light breeze.
It was clear: Aang was beyond the point of no return.
As he laid in bed, looking unnaturally pale and gaunt, Aang said his goodbyes. To Sokka, the overprotective goofball who proved himself as a competent strategist and swordsman, to Toph, the rock-solid teacher who pushed him to a limit no-one else dared to approach and reached a new peak in the process, to Zuko - a man who had spent months trying to kill Aang or to hinder his efforts to save the world, who proved himself as a virtuous and courageous ally when the end of the free world was nigh.
And his final goodbye was to Katara and Tenzin, the loves of his life. His wife who ran like flowing water, who freed him from the iceberg that had trapped him and given him the life that he lived. A determined, powerful woman, as unyielding and rough as a stormy ocean on a bad day and as refreshing and gentle as cool, lapping waves on a good one. The chill to his breeze, the yin to his yang. And his son - a remarkedly brave boy who faced solitude with determination, a believer in his culture. A child willing to continue his people's legacy, at the cost of having a regular childhood - a young man willing to bear the weight of his culture in Aang's place. Their place in Aang's life and their strength in such a stressful time brought tears to his eyes, and with the last few remnants of energy that he had, Aang wept with his young family.
In his last hours, unable to sit up, Aang gestured towards Katara that he needed to say something. As she leant down, Aang whispered into her ear.
"...Will you go penguin-sledding with me?"
Hearing his first words to her, delivered in such an earnest and lighthearted way in such a dismal situation, Katara choked out a laugh through her tears. She pulled away, but Aang raised his hand as high as he could to get her to stay.
"You know... I feel like I should have been around more for the first few years. I should've spent more time here with you instead of going off on my own so much."
He stopped to draw in a raspy breath.
"But even then, I feel like I did so much with the time I had. With all the villages I helped, and stories I heard... with every forest I helped to replant... I can honestly say-"
Aang coughed abruptly, and a tiny spatter of blood flew out onto his sheets. Holding back tears, Katara went to grab a cloth and dabbed at the area.
As she returned, Aang strained himself to raise his lips up to Katara's ear - and he rasped out what would be his last words.
"I honestly think, even with my regrets... that I... did everything that I wanted to do."
Having made his peace, Aang slipped into a peaceful sleep. It was only an hour later that he passed on, surrounded by his family and friends.
News of Aang's death spread around the world. News of his blockages had come out, spurring claims that he was never the true Avatar or that the Avatar Cycle was infected by evil energies - but aside from the few cynical sources of those rumors, the world at large went into mourning. Aang was honored as a hero that ended the Fire Nation's ongoing war effort against the Earth Kingdom, and his humanitarian efforts after the war were honored as well. Interest rose in the Air Acolytes as the world realized how close the Air Nomads were to dying, spurring a second wave of arrivals and an eventual emergence of the Air Acolytes as an individually managed group dedicated to the last surviving Airbender, as well as the family and friends of the Avatar, present and future. The Order of the White Lotus arose again, and the search for the next Avatar began. But Katara didn't care about any of that.
With Aang's death came a massive sense of emptiness. She spent weeks mourning, as did Tenzin - it was so hard to believe such a vibrant, unique part of her life had been taken so soon, it was as if a force of nature itself had been removed from the world.
But eventually, her surroundings sank in. She was surrounded by Aang - his mannerisms and customs were woven into every wall, every mural, every Acolyte. The orange and yellow robes that he had worn until the day of his death were around her every day, and he had even worked with a professional carpenter to recreate his original glider for Tenzin to use. The stories he had shared and archived in books were filled with his lighthearted energy, from the myths and lore of his people to his personal accounts of the war.
Even after his passing, Aang lived on through the work he had put into his surroundings. His memory lived on through every reconstructed village that honored the Avatar for his services, through every tile he set to restore his home, through the betrothal necklace for Katara that she wore every day until her own eventual death. His legacy lived on through Tenzin, the single Airbender left in the world, and through Tenzin's own family who would grow to define Air Nomad culture for the next hundred years. And the love and optimism that he felt for the world lived on through Katara, his loving and devoted wife.
It was Katara herself who predicted the world of change that Aang caused. Thirteen years after his century-long dormancy, and forever afterwards, it was clear to both herself and to history itself that Aang had truly saved the world and made it a better place.
AN: I was in a really bummed out mood when I made this. Nothing in my life really inspired it, I was just feeling angry and this angsty story idea felt cathartic to write. The idea took me back to 2006, when Avatar brought me into fandom and fanfiction, when I discovered how amazing and cathartic an angsty story would make me feel. In a way, it was therapeutic to write.
As you can tell, it's not canonical to Legend of Korra. I did borrow Tenzin, but having only seen the first season of Korra I didn't bother aiming for canonical accuracy. This is the sort of stuff that I'd read before TLA even ended, and I wanted to recapture that spirit. I hope you enjoyed it, please review if you did. Thanks for reading.