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."
"Apparently the only reason anyone could think of why I might name Mother's future mount involves my having given birth to it."
"Little enough. Volstagg has changed weapons again - she favours sword and shield now. Hogun got a new mace. Fandral has discovered the unfathomable charms of boys and talks of hardly one thing else once you get her started."
"Oh, boys. Has she simultaneously discovered choosiness and the fact that boys have personalities, or will arbitrary ones do, I wonder?"
"Hopefully she at least returns them undamaged whence they came. Is she the only one out of your circle who has discovered the marvels of the gentle sex?"
"If Hogun has, she's quiet about it, but then she is Hogun and never not quiet. Volstagg I doubt would notice a man did he not first cook her a good meal or three. I have not yet found one whose charms sway me."
"Nor I, but then I have been among people invariably followed by miscellaneous animals for the past three years, and by invariably I mean invariably, so it is possible something will change soon."
"I was just on my way to meet the Warriors Three in the practice halls. Perhaps it would please you to join us!"
"I would like that. Have you been practicing anything in particular of late? The last thing I remember was Volstagg lagging behind the rest of you in rolling with a fall."
"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?"
"I have learned one or two things, although I admit that giving birth to horses is very time consuming."
"Midgardians have a much different style, being weaker than we are and having less time to practice. What I have seen may be good for one or two surprises but will probably not suit for long-term repertoire."