She has the wyvern's tail barb fashioned into a dagger; it will produce no new poison on its own, and much of what it had leaked out when she cut it off the beast, but it remains particularly dangerous and will do for the first few times she uses it, and it's possible she will be able to refill it along the grooves through which natural wyvern-venom would have flowed if she finds a kind of poison she'd like to use.
Her mother honors her both with the gift of a new weapon, Lævateinn, and with the opportunity to name her peculiar eight-legged foal that she intends to ride into battle when he is older.
She calls the horse Sleipnir (he's a very cute foal, if... leggy...) and she's thrilled with Lævateinn. It's a glaive... and an axe and a scythe and a spear and a staff and a pitchfork and any other longish melee weapon she can think of; it will change in her hands, its length and blade and weight, as she likes. It is old - well, it's indestructible, and never needs sharpening; it has had every opportunity to become old - and now it is hers. She loves it.
Being an official adult is pleasant in many ways; in others it changes little; and in a few it is wearing and irksome.
But she doesn't mind being able to go along when the frost giants make incursions into territory on Midgard. Odin does not much care about Midgard for its own sake, as far as Loki can tell; she only wants the giants confined to Jotunheim. Loki's motives are different (and would not much matter even if they contradicted outright: princesses are supposed to show up on campaigns of war).
To Loki's immense convenience, the Asgardians outnumber the giants by nearly ten to one and no one she cares about in the least is lethally injured such that she'd feel obliged to mysteriously heal them. The giants are driven away and it is made clear that they are to stop harassing the short-lived people of Midgard.
Loki finds herself charmed by the humans. They're technologically primitive - the Asgardians like a low-tech aesthetic, are rather dominated by this preference, but that's not the same thing. They live and die in, not an eyeblink exactly, but a medium-sized period of time. They keep their souls outside of their bodies and shaped like animals, and the children's can change, which is peculiar but endearing.
The campaign is over in less than a week, and that long only because the frost giants are dug into the mountains. Loki's new toy gets plenty of exercise. She finds it useful to spear it into targets and change it before hauling it out of them, as long as she's not surrounded by many opponents; when she is, she does well to curve her blade for tripping. Her fallback is the favored glaive shape, but Lævateinn's ability to get longer is invaluable against such - well - giant enemies.
They win, the giants leave, the Asgardians prepare to go -
"Mother?" dares Loki. "By your leave I would stay here - no more than a few years. To explore. I am curious about the ways of the mortals and about their world."
(Now that she actually, really, truly has her permission to stay she is a little giddy about the idea of being so beyond Odin's sphere of caring-about-anything. She can probably do magic openly right in front of the Midgardians and nothing will happen.)
And then she notes her location and its nearby landmarks, and - goes.
She doesn't spend all of her time loitering around the mortals. There are animals to hunt (because she does need to eat) and landscape to wander. She uses flat illusions to process her thoughts and uses scarce notebook space only for things she has to remember later.
Sometimes she does go among mortals. They've got their genders back-to-front in these cultures (at first she thought they were going by the genders of their - "daemons", as they turn out to be called, but no, even when these match their humans, it is the men who fight and rule on Midgard), and they do no magic, so there is no advantage to being seen as the weaker sex while she's here. She goes about in male (adult, redhead, why not) guise most of the time, accordingly, although she thinks nothing of amusing passing children by revealing her true form if she happens to feel like it. Their daemons tell her a lot about their personalities. She sometimes neglects to display one for herself - let them think she has an insect hiding in her armor if they must - but sometimes she feels inventive and conjures up one that would withstand no touch but needn't fear such impropriety. Snakes and foxes and falcons and, once, when she is particularly whimsical, a small wyvern complete her disguise.
She is not a bard, but she does have access to stories they have never heard about fantastic faraway things well beyond the borders of the typical Midgardian's imagination, and these she tells - sometimes with embellishing illusions to set mood or illustrate visuals, sometimes unadorned. She tells them fiction and non-, neglecting to distinguish between them, sometimes filling in the latter with bits of the former where her memory fails or her audience looks bored, typically referring to herself in the third person when she features at all.
It is well past the point where she starts hearing her own tales recited by others in taverns and meadhalls that she realizes the Allspeak has glitched on her by reversing the genders of pronouns she utters, the mistakes thoroughly compounded by the local culture. They're talking about Odin the "Allfather", among other inaccuracies.
Her propensity for neglecting to stay put in her assigned gender has remained in these retellings, which is amusing until she realizes that someone has mangled the story of her naming Sleipnir thoroughly enough to believe her the literal mother of an eight-legged horse. The grasp on biology the Midgardians have is apparently negligible. She is put out but sees no realistic way to issue a correction.
She stays three years and two months, and meanders back to the Bifrost site, and calls out to be brought home. She loves it here - but wearies of conserving paper with such care, and longs to get back to her research and her sister and her tutors, even if it means being back within reach of Odin and Asgard's notions of right behavior.
She remembers to dismiss all her illusions first.
"She's much better now. This year we mainly spar with one another, and with whoever may dare to challenge us. Of whom there have been regrettably few in recent weeks. Have you learned anything on Midgard you could demonstrate? Or was it all hunting and singing and giving birth to horses?"
Loki usually loses to all of the Three. Especially Hogun; least so to Fandral, but even Fandral usually beats her. (Thor leaves them all behind, of course.) Right now Loki is fighting Volstagg. Loki wins one fight of four with her; but there is no reason it shouldn't be this one.
It's this one. Loki levers herself into the air with a cunning extension of Lævateinn and lands behind her opponent to land a decisive strike to her back.
"If you came all this way to see a Princess of Asgard fight, perhaps you should fight one," says Fandral, grinning at Thor and Loki.
"Perhaps I'm not ready to face such a worthy opponent," says the stranger. "One of their companions, maybe."
"Oh? Who would you challenge, then?"
"The talkative one," the stranger suggests.
Fandral laughs. "Very well then, I accept."
"That we shall!" says Fandral.
They draw their swords.
Fandral is quick - but somehow her blows never quite land where she meant them to. Fandral is nimble - but somehow she dodges into a strike as often as out of one. The stranger exhibits no polished techniques, no overtly successful stratagems beyond a gift for feinting convincingly, but somehow things just seem to turn out in her favour, again and again. She is either an unnervingly lucky swordswoman of middling skill, or a master of the art toying with Fandral for inscrutable reasons.
In response, the stranger drops her pretense of mediocrity. Her sword moves with blurring speed and exquisite precision. Fandral holds her own for ten increasingly dramatic seconds, and then the stranger disarms her neatly and stands back.
"I'm really no one famous, you know."
"The way you wield a sword, you should be!"
"Well, that's your opinion," the stranger demurs, but she sounds pleased.
"At least let me see your face so I know what to tell the bards."
"Bards like a mystery."
"Come on! I could almost swear I've heard your voice before..."
"You won't be any happier for knowing," the stranger warns.
"Nonsense!"
Loki keeps her distance - her weapon is, or can be, long enough to let her try for more tripping and spearing maneuvers than either Fandral or Thor tend to. She is trying to win, and she's seen him fight twice, but she knows how this is probably going to end.
When he eventually wins, he bows a graceful dancer's bow and then plops onto a bench at the side of the hall, next to the still-grumpy Fandral. She eyes him with irritated admiration. He smirks.
"Hey," grumbles Fandral.
"Are you not annoyed with me for being better with a sword than you? Or maybe I've got it all wrong, maybe your real problem is that I'm a better kisser."
"Hey!"
"I never said you're not good, mind. I just said I'm better."
"I can't imagine why, unless you demonstrate your appreciation for their learning by telling bards rude stories about them or perhaps poisoning their mead; it has been established that you have trouble identifying affectionate behavior." She turns Lævateinn into her usual glaive. "Will this do or should I start with something else?"
"Is that also how you manage pretending to be a woman?" inquires Fandral.
"Naturally."
"Obviously at some point in the process I must cease to believe that I am going to aim where I'm feinting. When? Where should I expect a failure to believe my lies to leave a tell - am I making mistakes in my facial expressions, my posture, my grip, the exact length of my weapon at the moment, my speed? When I do change directions, what can I do to make this more abrupt and difficult to compensate for - how do you choose a feinting target to match your real aim, and how do you change directions from one to the other?"
"How do you manage that?" wonders Fandral. "Don't you think about where you're really aiming at all? And if you don't, how do you remember you're feinting?"
"Well - have you ever felt like there's two of you? One doing the things you're doing, and another one watching the first one do them?"
"...no," says Fandral. "Not at all."
"Then I guess I can't just say I leave remembering up to the second Sigyn, can I."
"I was beaten by a mad boy," Fandral mutters.