Sadde's been meaning to go to one of those imperial capitals for a while now. He's tested himself around humans again, he's been only conjuring animal blood into his throat even though he could do the much tastier human blood and stay golden-eyed - there are in fact effects on his cognition, he notices them - and honestly even for a vampire this long moping is a bit much.
The fact that he thinks it's a bit much is probably as good an indicative as any that he's over it. It hurts that he's over it, but it hurts less than not being over it. He runs through the woods, so there's less risk he'll be spotted, and makes his way to one of the European capitals.
He stops when he spots a key.
He comes to a halt and peers at it. It's on the ground, half-hidden by grass, and there's a tree right over there that would have obscured his view had he been running a foot to the right. But as it is, he found the key. It is a very small key, as if sized for a child to hold, and it has a certain shine to it that's not quite like any other keys he's seen during his vampire life.
He explores a radius of about a mile around the key. There seem to be no houses or cabins or mansions or anything like that where such a key might have come from. He returns to it and peers at it, then shrugs and picks it up.
He doesn't pocket it, though, because the moment he touches the key he's quite certain it's a magical key.
It doesn't actually do anything, it doesn't explode or shoot fireworks or glow, there's no mysterious voice saying that he has found the Artifact of Doom or anything like that. He just - knows.
When he straightens up, he notices how he knows it. There seems to be a certain sense produced by the key, a feeling of sorts, that shifts and moves about as the key is moved through the air. He waves it around a bit, and reaches two conclusions: one, most spots in the air don't feel like anything; two, what a spot in the air feels like depends on the spot itself, and if he waves the key around a given spot multiple times he feels the same thing each time. Interesting.
Now what does the key actually do?
...well, it's a key, presumably it opens doors. It's a magic key - does it open all doors?
After thirty minutes - during which he runs to the closest town, finds the least observed door, and tries to open it with the key, followed by several further attempts on several different doors - he has determined that the key does not in fact seem to have the property of opening all doors.
He has also determined that locks consistently don't feel like anything to the key. Which seems to suggest that, if he wants to use it, it's not going to be on an actual door. So he decides to try the obvious thing. Except not here, this is not a good place, so he finds an isolated spot in the woods to try the obvious thing. Upon finding an appropriate isolated spot, he waves the key around until it feels like something, then he pushes it and turns it, as if he were unlocking an actual door.
That one works.
He pulls it, and the door opens before him. The scenery on the other side is subtly different, though similarly wooded. He removes the key from the door - it remains open, good - and walks through it.