Chapter Text
PROLOGUE
To Sienna, the lab was a cage, but it was the only thing keeping her heart beating.
The research facility didn't smell like the moss and damp soil of Pandora, it smelled of antiseptic, cold metal, and the heavy, mechanical hum of life-support systems. Her mother had been RDA, a woman who had chosen the wrong side and lost, leaving Sienna behind as a "souvenir" for the scientists to raise in the wake of the war.
"Your O2 sats are at eighty-two percent, Sienna. You’re pushing it," Norm said, his eyes glued to the flickering monitor. He adjusted the straps on her portable oxygen concentrator, his hands trembling slightly. "If you trip over that power cord one more time, I’m locking you in the cryo-bay! No running today. No climbing. Do you hear me?"
Sienna stuck her tongue out at his back, adjusting her exopack mask. "I hear you, Norm. I’m fine. I’m just... 'tactically slow,' remember?"
"It’s not a joke," Norm whispered, leaning down until they were eye-to-eye. "The prenatal damage to your lungs... the lab can only do so much. You’re dying, Sienna. Slowly. If you’d just stay in the pressurized ward-"
"No." Sienna’s voice was firm, despite the slight rattle in her chest. "I am not spending my life behind a glass wall watching the world happen without me. And you promised, Norm. You promised you wouldn't tell my Na'vi friends. If Neteyam and Lo'ak know, they’ll look at me like a patient. I just want to be their friend."
Beside her, Laveen, her caretaker and the human teacher for the Omatikaya, let out a soft snort, ruffling Sienna’s hair to break the tension. "Hurry up, kid. If we’re late, the Sully kids are going to start their adventure without you."
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Sienna was ten years old, a child born in the stars and raised in a lab, living in a world built for giants that her tiny, fragile body was never meant to survive.
By the time they reached the village, Sienna’s chest was burning. She parted ways with Laveen at the entrance, watching as the woman walked toward the "learning circle" where the village children waited for stories of Earth and the Great War.
With her "babysitter" gone, Sienna walk back to the forest, tiny feet bringin her toward the river. She found the troublemaker first, Lo’ak, his tail lashing with excitement as he tried to catch fish with his bare hands. Not far away sat his elder brother, Neteyam, focused and calm as he re-strung his bow.
Neteyam, only nine but already carrying himself with the poise of a future leader, looked up the moment he heard the ragged rhythm of her breath. His yellow eyes brightened, though he let out a mock huff as she approached.
"Hey, Skxawng!" she wheezed, leaning against a glowing tree trunk to steady herself.
Lo’ak spun around, a grin splitting his face. "Sienna! You’re late! I was about to go to the lab and drag you out myself." He hopped over, bumping his shoulder against hers with the rough, protective affection of a brother. "You look more pale than usual. You okay?"
"Just... the walk," she lied, forcing a smile.
"I heard you coming from the river, Sienna," Neteyam teased, his tail flicking in the grass. "You breathe louder than an ikran. How am I supposed to teach you to stalk a yerik if you sound like the sky rumbling for rain?"
Sienna gripped the straps of her oxygen pack. "It’s called... dramatic effect, 'Teyam," she wheezed. "I’m giving the animals a fair warning. It’s only polite."
Neteyam laughed, a bright, melodic sound. He stepped closer, noticing what Lo'ak had seen, the way her skin looked like faded paper, but he pushed the thought away. He figured humans were simply "faded" by nature.
"Where is Kiri? Is she with Tuk?" Sienna asked, stepping back slightly. The close distance made her self-conscious, she didn't want him looking at her face for too long.
"Taking care of the baby," Lo'ak answered, mimicking a crying infant. "Tuk’s been crying a lot lately. Pretty sure it’s her new hobby."
"Skxawng! Go help Kiri then!" Sienna shoved him, joining in the laughter.
Among the Sully children, Sienna was closest to the brothers. She loved their chaos and their spirit, even if her body forbid her from keeping up with them. She and Kiri were different. Kiri loved the quiet, and Sienna was a creature of the lab who craved the loud, wild energy of the boys.
"Come on," Lo'ak chirped, grabbing both of their hands. "Dad is about to talk to the warriors. If we sneak behind the longhouse, we can hear him explain the metal weapons again."
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The years that followed were a blur of bioluminescence and shared secrets. While Kiri felt the heartbeat of the world and Lo’ak hunted for trouble, Sienna and Neteyam were inseparable. He became her teacher, standing behind her to adjust her grip on the bow.
"Hold your breath," he would whisper, his hand steady on her shoulder.
"Easy for you to say," she’d murmur back. At fourteen, Neteyam was already a natural leader. He tried to include Lo'ak, but his brother was more interested in the guns and bombs of the Sky People than the traditional ways of their mother, Neytiri.
While the children moved as one pack, Neytiri never truly saw Sienna as one of them. To her, Sienna was a child of the Sky People, someone who belonged in the metal halls. Jake, however, welcomed her. She was the one who kept the boys in line. The one who reported back when Lo'ak was about to do something particularly stupid.
But as they hit their teenage years, the jokes about her breathing stopped being funny. Sienna became a shadow, watching from the roots of the Hometree, her portable tank hidden from view. Lo'ak thought she was becoming "lazy." Neteyam called her his "little sloth", a name he’d found in a human dictionary, thinking it was a cute description of her slow pace.
She took the insults with a smile. It was better than the truth.
°°••....••°°°°••....••°°°°••....••°°
The end came on a night when the forest was blindingly bright. While Lo'ak was back at the village getting an earful from his father, Sienna and Neteyam remained in the woods, stealing a few more moments together before her curfew.
They sat on a high branch overlooking a glowing stream.
"When I am Olo'eyktan," Neteyam said softly, his big hand finding hers, "I will build you a platform in the highest branches. You won't have to climb so much. You always seem so tired lately, Sienna."
Sienna chuckled, though the air in her lungs felt like lead. "I’m not Na’vi, genius! No way am I leaving my soft, fluffy bed at the lab."
"I guess I’ll just have to drag your bed to the Hometree then," he retorted. "Or... I'll build you a treehouse. Like the one in that book we read with Lo’ak."
Neteyam meant it. He wanted her there, away from the gray, cold walls and the smell of antiseptic. He wanted her to have no curfew and no limits.
Sienna didn't answer. She couldn't. All the running and laughing from earlier had finally caught up. The "rattle" in her chest was no longer a whistle. It was the sound of a machine breaking down. She leaned heavily against his blue arm, her gasps coming in short, terrifying bursts.
"Sienna?" Neteyam’s voice lost its warmth. He felt how cold she was. "Sienna, look at me. Is the air too thick?"
She looked up, her vision fracturing into a thousand pieces of light. She wanted to tell him about the disease. About the secret. About the blue body floating in a tank back at the lab that carried her DNA. But her voice was gone.
"Your breathing..." Neteyam whispered, his hands gripping hers as if he could squeeze the life back into her. "It’s... it’s stopping. Sienna, why is it stopping?"
The last thing she saw was his face. Not the face of the future leader who was happily talking about building her a hometree, but the face of a terrified boy who realized, far too late, that the girl he loved had been fading into the air for years.