Warnings: Shapeshifting/Gendershifting Loki; Explicit Language; Violence.

Notes:

The appearance of Female!Loki is based on actress Erica Cerra.

The appearance of Hel ('normal' side and general musculature) is based on actress Rosamund Pike.

The appearance of Fenrir in his human form is based on actor Santiago Cabrera.

As always, canon is pulled from here, there, and everywhere. The tone of this story may be very different from the first two, as it is the first in the series to be mainly narrated by Tony Stark.

Special thanks to my husband for being so enthusiastic about the first two fics and beta reading the third.

This fic will be updated once every 1-2 weeks depending on time and interest.


My Mark Upon Your Skin

He left his mark upon my skin

Said I've lost my loose heart

To the cold, cold wind

- The Mark, Cold Specks

-l-

Tony Stark never tells his lover what gender to be. Strange sentence, strange statement – most people don't tell their lover what gender to be because they aren't a big enough asshole to insist on a sex change operation – but Tony is dating a shapeshifter, so it's an actual thing that could happen, no scalpels necessary.

It would still make Tony an asshole if he asked.

Don't get him wrong, Tony is totally an asshole. But not about this. His lover, known to the world as Lori Silverton and/or Cold Iron, to the Avengers as the Queen of Air and Darkness, and to Tony as Loki Liesmith, has had people telling him…her… zir what and who to be zir whole life, and Tony knows what that feels like, how you fold up and collapse in, twist your guts trying to fit inside someone else's expectations. Maybe what they want is something you used to be, or something you never can be, but the point is that Tony knows what it's like and it sucks and also he's not stupid, he knows that Which form do you find more pleasing? is the shapeshifter version of Does this dress make me look fat?

So when Loki melts out of the shadows in Tony's room and asks what gender Tony would prefer tonight, Tony smiles and says what he always says. "I want Loki, however Loki feels like looking."

Loki smiles back, test passed until the next time the question is asked, and quirks a brow. "And if Loki is feeling blue?"

Tony's grin gets wider. "Then I'll do my best to cheer you up, princess."

Because fuck yes, Frost Giant markings have become one of Tony's kinks.

-l-

It has been not quite four years since Loki (found a home) returned to Midgard and resumed her guise of Lori Silverton, officially adding Cold Iron to the roster of Avengers. In that time Queen Pepper has married Tony's driver Happy (Loki was one of the maids of the bride and honored to be so, and created fantastical ice sculptures for the event) and become pregnant with her first child, Darcy Lewis has begun to positively pine over dear monstrous Bruce (though she thinks none of them can see), and Loki and Natasha have become what humans term Best Friends Forever. (But alas, it will not be forever. Not until Loki can arrange it to be so, and she has plans, many plans, she will not lose another child, not even her wish daughter, especially not her wish daughter…)

Loki and Tony have continued much as they began – experimenting equally with science, magic, and sex, creating many wonders even as they rain destruction down on their enemies in a hail of ice and plasma fire. Loki has a place, just as she always wanted, and it is here on Midgard with her High Priest and their shield mates, and Loki schemes and plots to keep all those things on this world that she considers hers just as she likes them.

Once such scheme is soon to come to fruition. For the past two and a half years, ever since an incident occurred in which her Tony was taken by enemies and hidden from her sight with magic, Loki has been weaving a spell. She cannot use the sigils of Asgard that bound the followers of Loki and Hermes to her in the old days (for they would draw the attention of Heimdall and Odin, and Loki will not risk putting any part of Tony's life in Odin's hands). She has instead been reacquainting herself with the runes of the Sidhe, for she is the Queen of the Unseelie, though she has rarely before relied so heavily on the powers that grants her. And yet, those runes also cannot make up the spell alone, for the power of the fae comes from the Crown of the Night Court, and should Loki ever lose the crown then she would lose Tony along with it…

So she stays up nights in the workshop with Tony, he working on his machines, and Loki weaving her spells. She studies each rune, the lines of power that feed it, and slowly, over time, she finds ways to change them. Learns to wield the magic of Jötenheim that runs in her veins and marry it with that of the crown.

She rushes, because the spell must be complete and placed on Tony soon. For now people remark on how well he is aging – he is almost fifty, which Loki has come to understand is the beginning of old age for humans – but soon he and others will realize that he is not aging, and in fact looks healthier and somewhat younger than he did several years before.

Loki would have him bound to her before he realizes, in case he takes it badly.

-l-

Tony is at a board meeting at Stark Industries and almost ready to climb the walls. Maybe fake a call for Iron Man. He'd gotten out of most of these meetings when he made Pepper CEO, but he's still the majority shareholder and also Pep's pregnant and he's supposed to be helping her out until after the squalling bundle of joy arrives (kids still make him nervous, he's glad Loki's are grown up and immortal and sort of Natasha). But that doesn't mean he's going to pay attention. He's physically present and sitting upright and they should all be grateful, which is of course why he's taken completely off guard and when he gets home Loki is going to kill him.

"Mr. Stark?" a sharp voice pierces the fog of his mental redesign of the Cold Iron armor (they're on Mark V now – there'd be more, but Loki gets stubborn when ze likes something).

He blinks. "Yes."

"So you agree it would be good for the company?"

Tony has no idea what they're talking about, but he's just supposed to be following Pep's agenda so she probably preapproved whatever it is and will get pissed if Tony throws a wrench in the works. "Yeah. Sure," he says, already drifting back into ways to make the leg joints and alloy flexible enough for Loki to shapeshift while in the suit.

There's smiling and clapping all around and Tony automatically smiles back, his press persona slipping over him.

"Excellent Mr. Stark!" some old white guy in glasses says as they all start pushing back their chairs. "We will look forward to the announcement of your engagement."

Tony nods and smiles and it's not until he's the last one left in the room that the words sink in and he almost falls out of his chair.

Forcing himself not to fly into a rage, he takes out his cellphone and orders JARVIS to play back the end of the meeting because JARVIS records everything.

And yep, that's what he thought. Tony just agreed that he should ask Lori Silverton to marry him for the good of the company because it's not like he hasn't been dating her steadily for years anyway (the shapeshifting helps, he won't deny it, being able to cheat without cheating), never mind that they're totally fine as they are and Tony is pretty sure Loki would have mentioned marriage by now if ze was interested and might be mortally offended when Tony brings this up because ze's a god (Tony's become a believer, sometimes he even prays) and Tony's a mortal and they're equal and not all at the same time.

This better not have been Pepper's idea.

(He knows it's not, he knows as soon as he thinks it that she wouldn't meddle like that, he's just being a dick and she's been all gung ho about marriage and babies lately and sometimes he doesn't know how to talk to her anymore.)

-l-

Loki is in zir side of the workshop when Tony gets back to the tower. Ze's wearing the female form that ze uses most often, since it's the one that everyone but Tony thinks is zir only form. Ze's leaning over one of the steel tables, chattering to the bots that roll around zir feet and Tony stops just to admire the way zir long black hair falls across zir cheek, the warm brown of zir skin and the cut of zir cheekbones. Olive green eyes flick up to meet his, and Loki smiles, a fierce, wicked thing that is the same no matter what face ze wears.

The lab door opens and Tony strides in, loosening his tie and shrugging off his jacket.

"Hey Snowflake. How's tricks?"

"Quite well," ze answers. "Now tell me what has you so agitated, Brightstar."

(Not even a minute and he's already busted.)

Tony doesn't even grimace at the nickname anymore, and not just because Loki always says it seriously, like a title ze's bestowed on him. He also doesn't bother to lie, because he can't lie to the God of Lies. Loki always knows, and sometimes ze counts the lies around zir, leaving everyone but Tony confused about the numbers ze announces seemingly at random. (The highest they've ever gotten in one night was two hundred and six, and that was when they were attending a conference at the United Nations.)

"I wasn't paying attention in a board meeting and after everyone else left I realized that I agreed to propose to you because getting married will be good for public relations," Tony says, not looking Loki in the eyes. He rolls his sleeves up and goes to see what Loki is working on, his hind brain screaming at him to run the other way all the while. But hey, it's not like he's ever listened to it before, why start now?

As braced as he is for some kind of temper tantrum (and Loki has thrown some memorable ones, though ze hasn't raised a hand to Tony since that time with the panic attack, back before Tony knew Lori was Loki), he is completely floored when all Loki says is, "Very well, but we shall be wed in the ways of both our peoples, and if you are to be my Prince Consort I will have to present you in Álfheim."

Tony freezes, mouth hanging open, and almost gives himself whiplash looking into Loki's face to see if ze is messing with him.

Loki laughs and comes around the table to plant a kiss on his forehead. Even in female form, ze is still a bit taller than him. "Don't gape at me so, my Tony. I have always intended to bind us together. I was merely honoring Midgardian custom in waiting for you to propose. It can be emasculating and frightening for a Midgardian male if the woman is the one to propose marriage."

Tony's ears are ringing and his heart is hammering against the arc reactor and he hears himself mutter, "You've been reading Cosmo again."

"I read that in Live Science, actually."

Tony laughs, and then he has arms full of Loki and he can think again and huh, it seems like everything is going to be okay.

Weird.

-l-

"So what does a fairy wedding involve anyway?" Tony asks after they have celebrated Loki's acceptance of Tony's suit with a bout of carnality.

Loki is male and naked and lying spread-eagled on Tony's bed, Tony equally naked and sitting next to him, idly running his fingers up and down Loki's spine.

"Since you do not have crests of your own, you shall be tattooed with the markings of my house," Loki lies. "Those of the Night Court, and those of Jötunheim. This will bind us together, and allow us to share our strength."

"Tell me you're not bullshitting right now, cupcake."

Loki rolls over so that he can look Tony in the eye. "I swear to you on the lives of my children that I have long planned to mark you as mine, and give you my strength in return in the manner that I have described."

That is true enough. Of course, this is the spell Loki has been crafting for some years, and it has nothing to do with marriage on either Álfheim or Jötunheim, but Tony has no way of knowing that. And presented to him this way, he will not feel able to say no.

Loki will not risk losing his love, his Tony, his priest (soon to be his druid).

Tony narrows his eyes, and Loki is sure that the Brightstar of his mind has caught that Loki's oath contains no mention of marriage. It is one of the reasons that Loki loves this man so. In Tony's vernacular, you can't bullshit a bullshitter.

But evidently Tony decides that he does not care enough to pursue the matter (yet another reason Loki loves him) and asks only, "What do you mean by share our strength?"

Loki sits up and pulls Tony against his chest, folding his larger frame around the man. He cards his fingers through that brown-black hair, smiling into dark eyes. Tony makes a noise, half protest, half renewed arousal. He does so love to be manhandled.

Voice deep and sensual, Loki murmurs into Tony's ear, even as his hands roam. "You will gain some of my physical strength, and heal faster, as I do." This is important, very important, for though Hel's blessing gave Tony the long life of an Aesir, he is still frightfully mortal and sometimes Loki wakes from violent dreams of Tony broken and bleeding, gasping for air. "With time and practice you will be able to call on my magic and wield it as your own, and I shall be able to draw on the arc reactor. And no one will be able to hide you from me, no more than they can hide me from myself." (You will never be able to hide from me.)

Shrewd Tony moans, his mind working even with Loki doing his best to distract. "Healing factor," he pants as Loki suckles the skin of his collar bone. "That means I'll age slower, right? Like Wolverine."

"Yes," Loki hisses, clutching at Tony's shoulders, eyes squeezed shut.

"Okay," Tony says. "Okay."