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Save him or yourself

Summary:

During a quiet night patrol, Peter Parker never expects his suit’s AI to call out to him. FRIDAY has flagged something wrong with Tony Stark—something far beyond stress. With the rest of the Avengers gone, Peter rushes to his mentor’s side, desperate to help.

But what he finds is no genius, no hero, no guiding hand. Instead, a poisoned bite has turned Tony into a monster—feral, unrecognizable, and bent on destruction. For the first time, Peter must face the man who taught him everything… and fight to survive when his mentor doesn’t even know his name.

Notes:

Heyyy guys!!!
So this is my first Marvel fanfic ever and I really don´t know how to write these things, so please excuse if it doesn´t make sense at some point or it´s too detailed.
English isn´t my first language so please excuse any grammar mistakes.
But nethertheless, I hope you enjoy whatever this is! Byee (btw i´ve come up with this idea bc i had a dream about it lol)
TW: Violence, fighting, sad (obv)

Chapter Text

The day was supposed to be a quiet one for the sixteen-year-old. In the morning, Aunt May woke him with one of her beautiful smiles and a hearty breakfast. Pancakes with maple syrup. His favorite breakfast ever since he was little. They talked about his upcoming exams and laughed a lot. If he could, he would stay with her forever, because he loved her—and she knew it, because he told her often enough.

When it was time for Peter Parker to go to school, he kissed his aunt on the forehead, stuck a pancake between his lips, slung his backpack over his shoulders, and stepped out of her apartment into the loud life of Queens. Even though the air was bad, and people were always shouting, honking, and cursing, he loved his borough of New York. It was his home, and deep in his heart it always would be, no matter where he might end up one day.

Happy was already waiting impatiently for him, and even though the teenager kept telling him he didn’t have to drive him to school and pick him up every single day, the grumpy-looking man always did. Because, if Happy was honest, he liked the kid. He was young, annoying, asked too many questions—but still, he had grown fond of him. Him and his aunt. Happy waved at her as she peeked out the window, and May smiled warmly back.

“Morning, Happy!” Peter called, his mouth full, still chewing on his pancake.
“You’re late, kid,” the man grumbled, tearing his eyes away from the woman at the window.

Peter tilted his head, glancing from Happy, who was now getting into the car, to his aunt, who waved cheerfully at him. Confused, he waved back, shrugged, and slid into the seat beside Happy.
“Sorry, but there were pancakes today. May makes them so good, I just had to enjoy them.” Peter apologized as he buckled in and the car started moving.

Happy only grunted in reply, but Peter smiled at him anyway before gazing out the window. Another trait of Peter’s that irritated Happy: no matter how rude someone was to him, he was always kind.

“Tony told me to pass on a message,” Happy said as the car came to a stop at a red light. Peter looked at him curiously. What did his mentor want from him? He checked his phone, but there was no new message from Tony Stark.

“The Avengers aren’t in the city today. Some mission—I don’t know what. Bruce is on the other side of the world working on some virus, and Thor’s in Asgard. Everyone else is out, except you and Tony. He also said he’d text you later to let me know whether I should take you to the Tower or back home.”

The Avengers weren’t in the city today?
“Thanks, Happy,” the boy replied, and you could almost see the gears in his head begin to turn. He liked the Avengers, and he believed the feeling was mutual.

With Captain America (who let him call him Steve—something Peter had thanked him for about a thousand times) and Black Widow, he often trained, and he lit up like a little kid every time they complimented him. (And really, who wouldn’t, getting praise from a super soldier and a superspy?) Sometimes he would just watch, quietly observing, making mental notes about their fighting styles, strengths, and weaknesses. They liked Peter. He was bright, strong, and impossible not to like. Curious, kind, always trying new things—like copying one of Natasha’s moves, or trying to throw Steve’s shield (and actually managing it once!). They hadn’t been thrilled at first to discover a teenager under the Spider-Man mask, but they accepted him quickly. And Peter, in turn, showed them how his web-shooters worked.

With Bruce, you could always have a good conversation. The scientist was thrilled with Peter’s sharp mind and happy to finally talk to someone about the most complicated theories. He didn’t even care that Peter was still a minor. He valued him as a team member and looked forward to working with him (which later proved to be true). While the others usually brushed Bruce off when he asked if anyone wanted to join him in the lab, Peter had been different from day one. When he’d first arrived at the Tower, asked for Bruce’s autograph, and gushed about his latest publication, Bruce hadn’t been alone anymore. Whenever Peter wasn’t with Tony or training, he came by the lab, and the two of them would experiment and debate absurd ideas late into the night. Bruce liked the boy with the sharp eyes that soaked up every bit of information he came across.

The impact drove every last bit of air from his lungs, leaving him gasping. Sharp pain tore through his chest, tears springing to his eyes. At least two ribs must have broken.

Hawkeye hadn’t liked Peter at first. In Clint’s eyes, he was still just a kid playing superhero. But deep down, the truth was simpler: Peter reminded him too much of his own children. Then, one day, he caught the boy watching him at the archery range with wide-eyed fascination. When Peter later asked in awe how he managed to shoot so fast, the ice wall around Clint’s heart began to crack. He showed Peter his technique, even let him hold his bow and taught him the right stance. That night, they played Mario Kart against Rogers, with Peter winning by a landslide, and Clint knew then that maybe he could like the boy after all. He swore to himself that he would look out for Peter as long as he could. He knew he could never protect him or be a father figure to him the way Tony was—but still, he wanted to do everything he could for him. And even though Natasha teased him about it, Clint couldn’t shake the feeling that he needed to help and protect the boy. He liked him. Just like the others did.

Doctor Strange and Falcon had agreed at first: the kid didn’t belong here. Too young to be an Avenger. But Tony insisted. Stephen found him annoying—too curious, too excitable. For Sam, it was simple: Peter was too young to understand the seriousness of it all. He cracked jokes when they weren’t appropriate, asked questions only a soldier would know the answer to. But Peter wasn’t a soldier. He was a teenager who went to school, had friends and family, and should be enjoying life—not risking it in battles he wasn’t ready for. But Peter was stubborn. Once he set his mind to something, he followed through. That was something Sam respected.

Stephen just wanted peace and quiet, and Peter’s constant questions drove him mad. When he finally snapped and told him so to his face, Peter had looked hurt and disappeared for the rest of the evening. But the very next day, he came back smiling and asked another question. Stephen had to give him credit: the boy was clever and strong. He saw it immediately—and somehow, he liked the attention his work suddenly got. A “thank you” here and there from the team had long since lost its shine. Nobody really noticed Stephen’s work. But when Peter started showing up after every mission, admiring his skills and praising his abilities, Stephen didn’t feel invisible anymore. He felt seen. And he decided he liked the boy after all.

By the end, both Sam and Stephen had warmed up to him. Sam still teased him about his age, but he always smiled at Peter’s stubborn comebacks.

Everyone liked Tony’s shy, brilliant protégé. Especially Tony himself. When he first heard of him, Tony was annoyed. Some wannabe spider kid in a cheap suit swinging around New York. And when he uncovered his identity? Even more annoying. Why did he always get stuck with the hormonal teenagers?

But then came that first mission. A bank robbery. Peter got hit by a car and shot at, and then he stood before Tony, bleeding and shaking. And Tony Stark’s heart softened. He helped him, built him a new suit, trained him, sent Happy to keep an eye on him, spent hours with him in the lab. And in that time, the boy had grown on him.

Tony had never really wanted kids. Pepper didn’t mind either. They weren’t planning on children anytime soon—and that suited Tony just fine, especially with his alcohol addiction. But when he looked at that boy with the brown curls and puppy eyes, and when he realized how much he cared for him, Tony knew he had a kid now. Not by blood—but still his. He loved that boy. With his innocent eyes, his shy smile whenever Pepper invited him to dinner, his endless gratitude whenever Happy dropped him off at home.

And before Tony knew it, he was three weeks sober. Then months. Peter Parker hadn’t just filled the missing role of a son in his life—he’d helped him crawl out of the bottle.

At night, when Pepper and Tony talked after Peter left, she gushed about him. How polite and sweet he was. How Tony better take care of him. And even if Tony didn’t always say it out loud—he loved that kid. His heart raced every time FRIDAY reported Peter’s blood loss or when his location went dark. He cared. When he officially made him an Avenger and introduced him to the others, Tony had been the proudest man in the world. And even though he’d caught a lot of criticism at first, he knew the others would melt for Peter just like he had. And he’d been right. They all loved Peter—just as much as he did.

His head slammed against the concrete ground, bones cracking. His own. His vision flickered, his skull pounding. Shouts echoed through the comms, Karen briefing him on his injuries—but all Peter could focus on was the face in front of him.
“Please… please stop.”

"Ned!” he called to his best friend as the boy scanned the cafeteria. When Ned spotted him, his face lit up and he grinned, rushing over to the table where MJ was already sitting beside Peter. MJ leaned lightly against Peter’s shoulder as she slowly picked at her vegetables, her eyes drifting over the other students coming and going. Peter brushed a dark curl behind her ear and gave her a small smile. She looked up at him, returned a faint smile of her own, then went back to eating.

Ned slid into the seat across from them and immediately launched into a rant about math class, which he had just before lunch. Peter liked math. He’d always been good with numbers. Ned… not so much.

“Can you tutor me tomorrow? I’ve got an exam Tuesday and I have no idea how I’ll survive it without you,” Ned begged.

Peter grinned at his best friend. “Sure. Eleven o’clock? You can have lunch at ours and then we can build my new Lego Star Wars set.”

Ned’s face lit up, and the two of them dove into an excited discussion about the new Lego collection.

The rest of the school day was about as spectacular as watching Steve Rogers try (and fail) to beat Peter at Mario Kart. By the afternoon, Peter was just glad to sink into Happy’s car seat and watch the birds outside the window. He was already looking forward to his nightly patrol, when he could finally swing from building to building. He loved that feeling. But most of the time, he only got to do it at night.

Happy dropped him off at home—Tony was busy with Pepper that evening but had promised Peter Sunday instead—and Peter thanked him as he got out.

“See you Sunday, Happy!”
“See you Sunday, kid.” Happy gave him a nod before Peter slammed the car door shut and jogged up the steps.

He let out a sigh of relief the moment he stepped into the apartment. May wouldn’t be home from work until later, so he decided to make some food and wait for her.

A few hours later, Peter was hunched over his homework when he heard the apartment door open.
“Pete! I’m home!” May called. He heard her drop her things and head into the kitchen. Since he had just finished, he closed his books, stood, and left his room to meet her.

“Hey, Aunt May. There’s lasagna in the fridge. How was your day?” he asked, leaning on the kitchen doorway.

May opened the fridge and pulled out the leftovers he’d saved for her.
“You’re a treasure, Pete. It was quiet today, not many new homeless cases. That girl I told you about, the one whose parents died—she was taken in by child services. Poor thing… but maybe it’s for the best.”

Peter nodded and told her about his day as they sat together at the table.

Later that night

11:02 p.m. Peter sighed, glancing up at the sky. Stars stretched across the darkness, the moon bathing the glowing city in a mysterious light. Even though it was late, New York’s streets were still alive with cars and pedestrians.

For half an hour, nothing had happened. Not a single crime. Karen hadn’t flagged anything either. Bored, Peter perched on the edge of a high-rise rooftop, pulling his mask down over his face. He inhaled the cool night air.

“Karen, tell me a joke.”

“Of course, Peter. In line with your Spider-Man activities, I have prepared one. Which person knows best what other people are missing?” came the AI’s monotone reply.

“Who?”

“A thief.”

Peter grinned, then snorted and shook his head. “That was so bad it was funny.”
“You asked me to make you laugh, Peter.”

He chuckled. Quiet gratitude bloomed in his chest—thanks to Tony, who had programmed Karen into his suit. Thanks to her, patrols weren’t so lonely.
“Thanks, Karen.”

Silence fell. Peter closed his eyes, enjoying the night. It was the weekend—he could stay up as long as he wanted. Patrol was his favorite thing.

“Peter,” Karen’s voice broke the peace, “FRIDAY is reporting elevated stress and violence levels detected in Tony Stark.”

Peter’s eyes flew open. He shot upright. “What?”

“FRIDAY is reporting—”

“I heard you, Karen. Where is he?”

Something was wrong. Tony never lost his cool. Not unless Peter went missing on a mission. But Tony knew where he was—he’d texted him earlier about patrol. And violence? Tony wouldn’t lash out, not like that.

“He is located on the rooftop of the Tower,” Karen replied.

Peter didn’t waste a second. He launched himself off the roof, webs shooting, the sharp tug in his arms swinging him forward. His pulse hammered with every heartbeat. What if Tony was hurt? Alone?

Stay calm, Peter. Maybe it’s just stress. Maybe…

But the thought crumbled instantly. FRIDAY wouldn’t sound an alarm for nothing.

The Tower loomed ahead, lit like a beacon in the night. Peter’s chest tightened as he pulled himself higher and higher until he finally reached the roof’s edge. He landed softly, crouched, then straightened.

“Tony?” His voice carried across the rooftop—careful, almost pleading.

At first, all he saw were the city lights, the glittering sky, the faint wind. Then his gaze locked onto a figure at the center. Large. Broad. Nothing like the Tony he knew.

“Oh no…”

The man—or rather, the thing—stood with its back to him. The silhouette was familiar and foreign all at once. Metal gleamed at the hands, but not like the sleek gloves of his suit. These were jagged. Claw-like. The movements were restless, twitching, almost animalistic.

“FRIDAY?” Peter whispered.

“Identity confirmed: Tony Stark. But… biological parameters deviate significantly. Warning, Peter.”

A cold shiver raced down his spine. That… that was Tony? His mentor? His hero?

“Mr. Stark?” Peter’s voice trembled. He forced himself to take a step forward. “Hey, it’s just me. Peter.”

The figure stilled. Silence stretched. Then, slowly, it turned.

Peter’s breath caught.

Tony’s face—or what was left of it—was twisted. His skin pale, with unnatural dark veins spiderwebbing across his cheeks. His eyes glowed with a sickly yellow light. Empty. Angry. His teeth—too sharp. Too wrong.

“Oh my god…”

Peter’s legs felt like lead. This wasn’t the man who helped him upgrade his suit. Not the man who told him he was more than just a “friendly neighborhood Spider-Man.”

This was a monster.

And yet—Tony had to be in there somewhere. He had to.

“Tony, can you hear me? It’s me, Peter. Your… your assistant, remember?” His voice cracked. He tried to smile, desperate. “You need help. Let me help you, okay?”

For a moment, the creature seemed to hesitate. A twitch. A blink. Hope flared in Peter’s chest.

Then came the growl. Deep. Vibrating. Wrong. It shook the ground beneath his feet.

The creature tensed—and lunged.

Peter’s spider-sense screamed.
“Tony!” he cried, leaping aside, rolling across the rooftop. Claws tore into the concrete, sparks flying where they scraped metal.

Heart pounding, Peter scrambled up. That’s not Tony. That’s not him. It’s something else.

But what if Tony was still in there, trapped behind the nightmare? What if he could be saved?

“Karen!” he shouted, dodging another strike. “Tell me there’s something left of him!”

“Data unclear. But I detect unusual neural activity. Possible Mr. Stark is still… fighting.”

“Then I can’t lose him.” Peter’s voice shook as he fired webs at the creature’s arms, trying to hold it back. “Come on, Mr. Stark! You’re stronger than this! Please… hear me!”

The creature roared, inhuman, ripping the webs apart with terrifying ease. Peter stumbled backward, chest aching. Fear mixed with agony and despair.

This was his mentor. The closest thing to a father he’d had since… since Ben.

And now he stood before him—not as a hero, but as a nightmare.

“I’m not leaving you,” Peter whispered, more to himself than to the monster. “No matter what happens. I won’t go.”

The creature charged again. Peter braced himself, every muscle coiled, ready for a fight he had never wanted.