A/N: A soulmate AU written for the Mischief and Mistletoe exchange on AO3, for Eternal_Love_Song. Thanks for reading!

Sif is in the palace with the All-mother the first time it happens.

One moment, she is striding down corridors at the queen's side, ensuring that all the palace occupants are unharmed after Laufey's attack. The next, she is floating through a night sky, surrounded by the light of a thousand stars.

And there, amongst the stars, is Loki.

Sif frowns. "What is this place?" she asks, voice echoing.

Loki glances around, brow furrowed. "If I let go, then how…?" Realization crosses his features. "Ah. I see."

When he says nothing more, Sif sighs. "And what is it that you see, Loki?"

"Well, my lady," he says, laughing, "we are soulmates."

"Soulmates? Loki, the only test of true soulmates is if – "

Oh.

"You mean…we are…"

"Sorry to disappoint. I'm sure you were hoping for some burly warrior instead, like my – " He cuts himself off with a sharp intake of breath, and his eyes flash dangerously. "Like Thor," he finishes, through gritted teeth.

"You think I am unhappy because you are my soulmate? Loki, you fool, I am upset because we are dead!" Her mind reels at the realization. Has she been killed in the palace, cut down by a frost giant? Or was it –

Oh.

It must be him, then, not her. Loki has died, and taken Sif with him.

"How did you – "

"Do not ask me that, Sif."

There is such hopelessness in his eyes – such pain in his voice – that she heeds his request. A moment later, he turns away from her, as if he hears someone calling him from afar.

Horror fills her when he begins to fade, his form becoming one with the darkness around them. "Loki!"

She blinks – and stumbles over her own feet in the grand hall.

Frigga glances back at Sif over her shoulder. "Are you alright, dear?"

"Y-yes, my queen," she stutters. Frigga gives her a strange look, but a voice calling for help down the hall distracts her from questioning Sif further.

Later, when Asgard mourns, Sif cannot bring herself to cry. Not when she knows the truth.

Loki lives.

The second time it happens, she is sitting on the floor of his old cell, back pressed to the wall. After the elves' attack yesterday, there are very few areas in the dungeons still intact. Of course, Loki's cell is unharmed, she thinks. Save for what he destroyed himself, that is.

Beside her, Fandral thumps the back of his head against the wall, over and over. "Well, this will be a grand tale for the children, eh, Volstagg?"

Volstagg continues to pace before the enchanted glass. "You don't think the All-father will keep us here for long, do you?"

"Most likely, we'll spend a full day and night for our treason," Sif replies. She grins at Heimdall, who is seated on her other side. "It was worth it, though."

Her brother smiles back at her. "Indeed it was, sister. The princes face Malekith now, Jane Foster at their side."

She is about to reply, but the world around her suddenly twists, spinning until she is back in that strange space again. The stars burn around her, seeming to somehow be both close enough to touch and countless realms away. Her gaze immediately meets Loki's.

"I'm sorry, Sif. It was the only way to save Thor – to save Jane."

"What happened?"

"The creature from the attack yesterday, the one who – " He breaks off abruptly, the rage clear in his eyes. There is guilt there, too, beneath the rage, but he hides it quickly. He continues, "The one who murdered my mother. It was ready to kill Thor, but I – I stopped it. I killed it first. With its own sword, mind you. I thought you might like that."

She laughs despite herself. "You are right. I do."

He gives her a small grin, one that does not match his next words at all. "Then it ran me through with that same sword, still protruding from its chest, and covered in a sickly poison from its blood." He laughs madly. "And so I died, as did you. My apologies, dear Sif, that you must be bound to such a monster for eternity."

"Do not call yourself a monster," she admonishes fiercely. "The creature that you defeated today? That is a monster. Though you have done monstrous things, you have never been a monster, Loki – no matter where you were born."

"Ah. So you know the truth, then. Tell me – is all of Asgard privy to my darkest secrets?"

"Thor told me, no one else. He thought that I deserved to know, after – well. After the years that you and I courted."

He rolls his eyes. "And he did not think it my story to tell?"

"He thought you were dead."

"But you knew better. And yet, you chose to remain silent. Why?"

She stays quiet for several moments, studying him intently. "I thought it your story to tell."

Loki grins. "And that, my lady, is why we are soulmates." Reaching across the space between them, he takes her hand in his.

Sif blinks, and she is back in Loki's cell, looking at her brother.

Heimdall tilts his head, curiosity in his eyes. Sif panics. He must have seen her disappear from here, though no time has seemed to pass in the real world. Could he see her even in that place she shares with Loki, caught somewhere between life and death?

More importantly than that, has Loki cheated death a second time?

"If I live, so does he," she whispers, accidentally speaking out loud.

"What was that?" Fandral asks.

Sif's panic grows. Before she can fabricate a reply, Heimdall rescues her. "They have reached Earth. Jane Foster's friends plan to help them."

He does not say a word about Loki.

Volstagg claps his hands together. "Excellent! Now…Loki must have left a snack lying around here somewhere, right?"

Fandral laughs. Sif gives her brother a nod of thanks. He returns it, and – thank the Norns – keeps silent.

Even Sif, the goddess of war, cannot help but think that dying a third time is excessive.

"I am growing rather tired of this, Loki."

He laughs. "And you think that I am not? At least you do not suffer the physical consequences."

She eyes the massive bruise that is already visible on his neck. He has a point. "So this is it, then."

"Hmm?"

"Surely there is no return to life for us this time. From what you have explained, Thanos has been…thorough."

"You wound me, Sif," he says, placing a hand over his heart. "Do you truly think that I would face my greatest enemy without a plan?"

She raises an eyebrow in question. "And what would that plan be?"

Loki grins. As if at his command, his form begins to fade from view, bringing him back to the realm of the living. "Find me, and I will tell you."

With a jolt, she falls into the pilot's seat of her ship. The viewport tells her that she is still near Nidavellir.

Loki, posing as the All-father, had sent Sif on a quest throughout the nine realms to see if any needed Asgard's help. Discovering that Nidavellir was abandoned, she had planned on returning to Asgard immediately with the news – but Loki's third death interrupted her mission.

Now, with a heavy heart, she knows that there is no Asgard. Asgard was destroyed, her people slaughtered by a maniac who offers only pain and death to those who oppose him. Thor is lost in the cosmos, alive but broken. Heimdall, her dear brother, is dead, no more than golden dust scattered amongst the stars.

Yet Loki has somehow outsmarted death for a third time.

Straightening in her seat, Sif enters the coordinates for Midgard into her ship's navigation. She knows Loki better than anyone – and for a reason she cannot explain, she knows with absolute certainty that she will find him there, among the humans he once tried to rule.

Loki's plan will be brilliant, but dangerous. She doubts that he can escape death a fourth time.

His last words ring in her mind. Find me, and I will tell you.

"I will be there, Loki," she vows. "I swear it."

Whatever his plan, he will not have to carry it out alone. This time, she will stand at his side.