To understand MCU time travel in the context of this work, see the bottom for notes. The fic might be a little easier to understand if you do. If you don't want to know the details, no worries. Just know that when I say time travel does/works/creates something, that it does :D

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Chapter 1: I Died, Right?

Pepper's voice echoed in his ear, sounding both next to him and very far away.

"You can rest now."

Tony's vision went black and the next moment, everything was different.

The first thing he noticed, naturally, was that nothing hurt anymore.

The next thing he noticed was that Pepper, Peter—everyone—was gone. In their place was a rolling, golden fog, shimmering at the edges with red and green sparks here and there in the corner of his vision.

"Honey? Peter?" he called out, staggering to his feet.

Huh. Well at least he was able to do that.

Was this heaven then? Or Thor's Valhalla? It was a bit boring, but it was rather pretty, he supposed. He didn't hurt, so he didn't think this was hell at least.

He didn't really know what to think or feel, so he just stood there for a few minutes, waiting for something to happen.

Nothing did.

Well, he wasn't getting answers here; he might as well explore a little.

He took a step, and then froze, startled.

Looking down, he realized his clothed arms and legs looked somewhat… ghostly.

He could see through them, and they almost blended in with the rolling fog around him. His feet were barely visible, and—even more astounding—they weren't even touching the ground.

Okay… well this was definitely the afterlife then.

"You're not dead."

The voice came out of nowhere and Tony whipped himself around.

In front of him sat a young woman. Technically she was also floating, about an inch off the ground. She had shoulder-length brown hair, slightly curled, and mischievous brown eyes, glittering with amusement. She was wearing leggings, and an odd sort of loose robe with deep pockets. The robe was red with golden accents: iron man colors. Tony couldn't help feeling that he'd seen her somewhere before.

The woman was also ignoring him, looking at several tablets she'd spread out around her, switching her focus from one to another every few seconds.

"Have I met you before?"

"Actually you haven't. The other me, but not me."

Tony frowned, "What's that supposed to mean?"

The woman rolled her eyes, "Ha. And they call you a genius. Told Mom you wouldn't know. Actually, stay there for a sec will you? I need to do something."

Without further ado, she pulled out an odd piece of jewelry—it looked like two gold rings attached by a flat strip of gold alloy—and drew a gold circle in the air, exactly like the ones he'd seen Strange create on the battlefield.

She waved a hand and suddenly, he was looking at himself.

It was a body, laid out before him with eyes closed, covered in cracked pieces of armor. Half the body, though dirty, appeared relatively fine. The other half of the body looked like it had been burned to a crisp.

That body was undeniably his.

Tony decided he'd had enough experiences in the last few minutes that made absolutely no sense.

"What the fuck is that?" he asked.

The woman held up a finger, scrolled through several screens around her, and then took a syringe filled with a glowing green liquid out of her pocket, "I said stay still for a minute Da—er, Tony."

Tony, oblivious of her slip of the tongue, watched her move to inject the still body in front of him, "Are you sure that's such a—"

She pressed the syringe before he could finish speaking, and he felt a pinch above his right elbow.

"Ouch," he said, rubbing the spot on his current, ghostly body, looking down at the still, solid body below him.

"Sorry," she said, before waving her hand, and making the body disappear once more amid golden sparks.

There was silence then, as the woman sat still, floating quietly, apparently done with whatever task she'd just accomplished. Tony found the stare a little unnerving, but he didn't look away.

"You look so ridiculously young. It's really weird," she said at length, wrinkling her nose.

Tony raised his eyebrows.

"Young?" he spluttered out, "If I'm young, what are you? You look, what, twenty-five?

"Twenty-seven," she replied primly.

"My point stands."

There was another silence.

Tony groaned and pinched the bridge of his nose, "Look lady, I've had a really stressful day. I time-traveled, reconciled with my long-dead dad, helped bring my semi-adopted son back from the dead, fought a battle with fighters teleported in from all over the galaxy, and, oh yeah, I died. Is it too much to ask for some straight answers around here? Let's start simple: where am I?"

His companion grimaced, "That's, actually, particularly complicated."

Tony rolled his eyes, "Of course it is."

"How about we start by explaining my first point, and go from there?"

Tony frowned, "You're first point being?"

"You're not dead."

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Okay so notes:

Everyone on the internet seems to have different theories/ideas/issues with the MCU's version of time travel. I wanted to explain how time travel works for this story.

This is the theory I'm going with:

In the MCU, for this fic, I'm gonna say time travel has 4 rules:

1. Whenever anyone travels to the past, it immediately creates an alternate timeline from that point on.

-The simple fact that you breathed an extra amount of oxygen on the planet means that a whole new timeline has started. Everything from the timeline you've traveled from (meaning your past) stays exactly the same. That's because any changes you create simply change this other timeline you've traveled to, (an alternate reality if you will.)

2. Returning the stones ensured that all the "good guys" of the MCU in these new alternate timelines had the infinity stones as weapons against Thanos.

-However, that doesn't change the fact that they are still alternate timelines. For example, there's an alternate timeline still happening where Loki got free and managed to get the tesseract after the Battle of New York. There's also a timeline where Thanos, his army, and his daughters just randomly disappeared when they came to our reality.

3. At the end of Endgame, Steve jumped to the original MCU timeline, but only after he got really old.

-He didn't live out his life in the timeline of the MCU movies. He lived in an alternate timeline/reality, got old, probably waited until Peggy died, and then jumped back to the MCU original timeline.

4. Changing something in an alternate timeline/reality doesn't necessarily make it better or worse. It simply changes it.