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—
"There's usually several in a week, sometimes a few a day. Sometimes more if there's some coordinated multi-demon effort."
So he goes and does that.
"If I erase part of a used up circle and complete it again, does it then become a new circle?"
"Nope. But if you make it out of, say, drizzled sand on the ground, you can reuse the sand if you gather it all up."
"What if I successively replace parts of a circle with new parts, does it count as a new one after I've replaced all of it?"
"I don't remember trying that, but maybe I did..." He fetches his computer and looks up his notes. "No, I did not try that particular experiment as a summoner."
"I took really good notes, do you just want my project notebook from when I first discovered summoning?"
Cam hands it to him. It opens with a recounting of how he found this weird book in an abandoned mansion and tried something in it just for kicks and holy fuck it worked and now he's going to make a serious study of the thing.
There's notes on what transpired when he talked to the angel summoned out of the book he found, and then there's notes on the rest of the book as he read it, and then various interviews and tests with other daeva.
And then there were speculations on what fully scaled-up daeva summoning would do for the world and the beginning sketches of a plan.
Sadde himself would've probably spent more time testing, but maybe Cam's way worked out better.
But then Revelation!
Cam tosses him a sequel notebook; apparently after Revelation Cam pretended to have been a garden variety summoner driven into the open by the publicity and he taught summoning at a university until he died.
"Yeah, he got arrested, I followed the coverage from here. I don't think he wound up in Hell, he's probably an angel or a fairy now but I didn't follow up."
"I didn't know until I died that summoners went to daeva realms. There were so few summoners before Revelation; nobody I talked to knew, or anyway they weren't talking. Afterwards, well, I was a demon, nobody let me have a phone call."