Tony Stark is immortal.

They call Thor immortal, but that's not true. Thor is only immortal in comparison to humans. Thor can and will die, just a few thousand years later than everyone else.

Except Tony. Because Tony can't die.

Well, okay, that's not quite true either. Tony can die. He just doesn't stay dead.

At least, that's what the man with the long coat told him when he was six. Tony hadn't believed him at the time.

When he was twenty-three, he was stabbed by a woman in a hotel room. Thankfully, she was already gone by the time he woke up, and Tony was left to wake up in blood soaked bedsheets without a wound and panic.

Two years later he was hospitalized for alcohol poisoning. The doctors told him he was extremely lucky, that his heart had stopped beating for a moment but they'd managed to resuscitate him. Tony wondered.

No one else was there when he died in an explosion in his lab, the toxic chemicals killing him before he had a chance to react. Only his own security cameras caught the footage of him waking up again in a flaming lab, completely unharmed. The footage was destroyed and Jarvis would never betray his secret.

After that, Tony started taking more notice. He'd accepted that he couldn't die – although he wasn't planning on testing that any more than necessary. Injuries didn't last long either. He burnt half the skin off his hand once, and watched as it grew back in less than an hour. After that, he started being more careful. People would notice, one day, and then he'd be locked up, experimented on. He was a freak, and he couldn't trust anyone with his secret.

He died in Afghanistan when the bomb hit. He died on the operating table in the cave when they were digging into his chest. He died once in the desert of dehydration and was close to dying a second time when Rhodey found him.

He died on the rooftop when the arc reactor blew, just about gasping back into life by the time Pepper reached him.

The arc reactor in his chest caused the most problems. He couldn't get rid of it without revealing his secret. And then the damn thing started killing him slowly and painfully through palladium poisoning. He didn't actually die, he cured it first. But people had noticed.

He would never forget the day that Pepper found out.

()

He'd been on a mission in the Middle East, and he was losing blood fast. He told Jarvis to get him home, so that he could die without anyone realising.

Except Pepper was at home. He was soaked in blood when he finally got the suit off, his skin deathly white, and he crumpled to his knees.

He heard Pepper before he saw her. "Tony! Oh my god, Tony! Jarvis, call an ambulance. Tony, look at me! Where's the wound, what happened...?"

Her hands were pulling at his clothes and Tony forced his eyes open, his heart clenching as he saw the tears on her face. "No ambulance," he muttered, hearing Jarvis acquiesce. He grabbed Pepper's hand before she could tug his t-shirt away from the bloody wound, squeezing it weakly. "S'okay..."

"No, Tony, no..." Pepper interrupted, before Tony could explain. "You'll be okay, you have to be okay..." She was almost sobbing now.

Tony's vision blurred. "No, s'okay..." He took a deep breath. "''M'sorry, I didn't tell you..." His world blacked out to the sound of her sobbing.

He woke with a gasp, his body aching terribly for a moment, as it always did, his lungs burning for air, before he noticed his surroundings. He was covered in his own blood still, and he was lying half in Pepper's lap. And she was staring at him.

Tony groaned, sitting up. "How long was I out?"

Pepper was frozen, mouth open as she stared. "You... you died..." she said, voice shaking.

"Ten minutes, sir," Jarvis added.

Tony winced, turning to face Pepper. "Yeah. I... I can't die." He wasn't going to lie to her now, but he looked down at the floor.

Pepper didn't answer, and Tony's stomach churned with nerves. She was going to hate him, she was going to leave him, this was it, he was a freak...

"You what?"

"I can't die. Well, obviously I can. I just did. I just... I don't stay dead. I don't know why. But I mean, it's happened enough times now that I'm pretty certain..."

"Tony." The tone of Pepper's voice forced him to look up.

"I'm sorry," he added lamely.

She frowned at that. "You're sorry that you didn't die?"

"What? No, of course not." Tony made a face. "That I didn't tell you."

There was a long moment of silence, and Tony watched as Pepper tried to process this.

"So... a couple of months ago? You weren't actually dying then?" she asked carefully, and Tony can hear her confusion.

"I, well, I was dying. But I'd have come back. I assume. But I never know. I mean, I don't know if this lasts forever or if I've only got a hundred chances or something. I didn't know how to tell you."

"Yeah, I can see why you didn't tell me." But Tony could tell she was still hurt, and he looked up quickly.

"It's not you Pep, I promise. Nobody knows." He shifted closer to her, to pull her into his arms, but she shied back.

Tony froze, his heart sinking. This was too much for her. He was a freak. He'd lost her. He sat back on his heels, looking down and trying not to cry. "I'm sorry," he muttered. "Just, look, please don't tell anyone. I'll keep out of your way. You don't have to see me again. I'll sort something out..."

"Wha—Tony, no. I'm not breaking up with you!" She sounded horrified, and Tony looked up, hope blazing suddenly again.

"You... you're not?"

Pepper smiled slightly. "No. I mean, we have to talk about this. There is... this is huge. But no."

"I love you." It was the first time he'd said it out loud, and he blinked at her in surprise. He didn't register Pepper moving, but a second later she was in his arms and they were clinging to each other. "I love you too, moron."

()

Tony died in New York. Hulk's roar was timed perfectly and everyone thought that that had resuscitated him. That wasn't what had scared him and Pepper. No, it was the thought that if he hadn't fallen back through the portal he would have been floating in space for all eternity, returning to life only to die instantly without oxygen. He couldn't stay in New York after that.

Tony knew that one day, Pepper would die and he'd be left on his own for as long as he lived. He was determined to make sure that didn't happen early, that she lived as long as she could. He had to protect the one thing he didn't want to live without.

Then he failed to catch her and she fell into fire. They thought it was extremis that had saved her.

A year later, after Tony had gotten rid of the extremis, there was a sniper. A bullet whistled through the open window in their vacation house and Pepper fell.

Barely three minutes later, she woke up in Tony's arms with a gasp.

Living forever wasn't something Tony had been looking forward too.

Forever with Pepper... well, that was something he could get used to.