Sadde's running.
Not for any particular reason, just because it's faster. He's been meaning to go to one of the capitals for a bit and now, he supposes, is as good a time as any.
And eventually he's not running anymore, because he's close enough to civilisation that someone might spot him. Not that he wouldn't be able to notice them by scent before they saw him, but still. And as he makes his way to the Norway capital at this more leisurely pace, he notices the tiny, shiny key. He walks towards it and picks it up and immediately notices just how magic it is. He can tell by the way the key feels like things, and different things depending on where it is.
He verifies that what the key feels like is consistent in absolute location by waving it around a bit and seeing that the same place always feels the same. "Huh," he murmurs to himself.
He straightens up and thinks. The first obvious thing to try is seeing whether it opens any doors—a universal skeleton key sounds like the kind of thing a magical key could be—but the second obvious thing can be tested right there and then. He pushes the key into thin air with some purpose, as if he wanted to unlock an invisible door, and then turns it, et voilà, the faintest of door-shaped outlines appears before him.
He locks the door, and it disappears. Unlocks it again, and there it is. So he pulls it open and sees—
Sadde helps along with biokinesis, and the wings fall off, and she lets out a breath she'd been holding—being partially human is weird—and slowly calms down, enough to explain: "Turning is a very painful process. It lasts three days, the venom reforms our whole body. I—should've expected this to happen, once the venom got into contact with it." She says it all in a small monotone.
"But this doesn't happen when you just - squish or desquish yourself..." Hug hug hug.
Hug! Cling. "I guess I'm not turning really human? I don't know, I don't actually know what's going on on a biological level, my power's awareness of what's going on is less specific than that. Maybe it's because my blood vessels are already dealing with the venom, maybe I'm just mimicking a human body, I don't know."
"Yeah, I'm fine now. I might want to try my hand at designing my own pair of wings, though. And if that fails, um, can I ask you to hug me throughout the process?"
"Turning the whole way, yeah. If it's just the wings, I think a few hours, from the way it started and their size. I can grow a tail myself, though, I've done that before."
"I'll try growing a pair anyway and see what I can do." She looks at the severed pair and hmms. "I wonder if I could turn the wings separately and then just—attach them to myself?"
"Can you make new ones attached to, I don't know, a circulatory system or something that will keep them alive for long enough for the venom to turn them? They should have my DNA for me to be able to properly attach them to myself but—I should probably just try making my own before anything."
"Oh, uh, demons can't make minds but we can make bodies. Result is kind of creepy, so if that's the sort of thing you have lying around you keep them in the basement if guests come over."
"Okay one, that sounds useful for this particular problem, but two, why can you not make minds?"
"No idea, just seems to be a hard magical limit, but I'm kind of glad we can't, can you imagine? Right now the equilibrium in Hell is that everyone is indestructible and has fantastic magical powers and can instantly replace anything of theirs you destroy. Imagine if anybody who felt like it could make an army of second-class citizens."
"Well, but, suppose you actually specify a brain in all its details, down to the cellular level, or maybe even molecular if that's necessary. Would that fail to have a mind?"
"There are no detectable flaws in the copy when we copy a human brain. We just get a basement dweller. It affects animals too, anything smarter than like a snail will be pretty clearly stupider than it's supposed to be. And fortunately at least in humans there's enough mind/body interaction that we also can't get female basement dwellers to carry to term and get Hell-dwelling humans that way, although we can get, like, cats, so there are cats."
"Hmm, I'd suggest something relating to souls but if even cats have basement-dweller problems... Do cats go to Limbo?"
"Not usually. When a person goes to Limbo, they get approximately their favorite thing, and that's sometimes a pet. Those have roughly normal intelligence for the species, it seems to these people like the pet has continuity with the live version if applicable, and they get indestructibility too - stuff in Limbo in general does in a kind of cool way, like, if your Limbo thing is a house you can give away everything in your fridge and find bacon there the next morning, run the water constantly with no real plumbing, etcetera."
"Hmm, can you make quantum computers? Can you copy quantum information?"
"Uh, our computer science didn't wind up going that direction to any significant degree..."
"When I'm from they're mostly speculative too, but there's people who think brains might be quantum computers and there's a theorem called the no-cloning theorem which says you can't create a device that can copy arbitrary quantum information."