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—
"But I don't have a Monopoly set and this is clearly an insurmountable problem." Wag wag wag.
"Help me out, here, I don't trust my brain to reach correct conclusions about body language that includes a tail, all I can think of is pouncing on you and doing blasphemous things to your body."
"I'm pretty sure you cannot technically blaspheme by doing things to a demon." Wag wag wag wag. "You'll figure out the tail eventually."
Good she interpreted the body language correctly! And since it's been way too long since they last had sex she will start with neck nibbling.
Good, then she will go ahead and do that, and then proceed to do it to herself.
On one of the coffee breaks, she says, "I think my wings are probably properly vampired."
"Probably. We can go see if you can attach 'em. Do you have philosophical objections to then dumping your basement dweller into the black hole? I don't particularly want to feed it."
So they haul the basement dweller out of the closet and Cam interpolates its wings off and offers them to Sadde.
And so:
success!
"Congratulations! Should I grow a tail on the same one or are you all set for now?"
—and falls on his face.
"...Learning to fly takes practice," says Cam, dragging the basement dweller to the large central garbage chute.
"So I'm gathering. Well, I'ma grow a tail, then." So he does, black with short fur and an arrowhead-like end.
He wags his and grins. "Is there a standard set of tail-language I'm gonna have to learn?"
"Not really, wings are all at least loosely alike but there's many kinds of tails and they move differently. I've basically got 'wag' and 'lash' and 'startled twitch' and 'wrapping it around your leg'."