She inserts the key into a lock that's not there, in the air, and unlocks a door that wasn't there before she did it, but now it is, made of a faint outline. She pushes.

And they're in space.

"Oh man, oh man, this is real. None of the alerts are beeping... What even is that place?"

"Oh that's right you guys don't have planets. So in my world—and, I expect, most worlds, because it's simpler—anything with matter attracts everything else with matter. And that's what we call gravity, instead of there being a universally-recognised-as-down direction," she starts explaining.

He gets a stick with a grabby claw on the end from a rack on the back wall and messes with the control panel again while she talks.

And she explains planets and the Earth and stars and spaaaaaaace "and this is probably a world like mine," she finishes gesturing at what they can see through the door.

A faint translucent wall appears on the ground between them and the door, all across the room. "You say that's vacuum beyond that doorway? Think air will rush out if we poke something through? This setting blocks everything but marked tools, including air. Potions department loves it."

"One of the noted perks of my species is super heightened senses. I noticed when I walked through the door the first time, the door doesn't let air just go through, even when I did go through it. I'm pretty sure nothing will happen."

"Oh, that's slightly disappointing. Vacuum is neat. Mind if I stick a sensor thing through for a moment anyway?"

"Go ahead."

So he does, and giggles when his reader squawks about the pressure.

"Okay, that's pretty cool. I think I can tentatively believe you."

And then he remembers what exactly he's believing and blushes again.

Oh dear he is way too cute she could just—

No she could not she will not do anything he doesn't want—

"My world is also far less academically secretive than yours," she offers instead.

"Probably a good thing. It was such pain trying to figure out if anyone had done golem memory already!"

Shiny wall goes down. Tools go back on rack. "Close it? Exploring other worlds would be neat but not without prep."

She closes it, locks it, and the outline disappear. "I have slightly fewer self-preservation instincts than you do. What with being generally immortal, not needing to breathe, being very durable, super strong, and having neat individual magic that gives me stuff like," and she flutters her wings a bit.

"Oh, so vankires don't have wings naturally?" The humming stops and he heads back for the elevator. "Immortal in a Fate sense or in a dragon sense? ...Dragons don't get old. Fates respawn." 

"Hmm, I'm not sure how durable dragons are. Vankires don't respawn, but we don't age, can heal from pretty much any wounds you can imagine, we're really strong and fast, eidetic memory, faster brains, roomier brains, super senses, no need for breathing or sleeping, never get tired at all, only way to actually kill us is dismembering us and setting us on fire. Plus in my world some people have individual magic, and some people don't but they get some when they turn. My wings are part of a general biokinesis package, I can shapeshift and generate endless biological matter."

He gives a low whistle. "That's an impressive list! Now the uh, mating thing, since I'm fairly confident you're being honest, are there any examples of it going wrong?" He's still going to treat her answer with skepticism, but.

"—yes. Except not wrong in the sense of, erm. Like, only vankires mate, not hybrids—humans and vankires can have children that have lots of the same perks—and if a vankire mates on another vankire it's always reciprocal and symmetric. If they mate on a human and the human turns it becomes reciprocal and symmetric. If the human doesn't turn, or if they mate on a nonhuman, then... it can, er, not work out."

More information that pushes for him to 'turn'. It all seems to line up nicely. "Funny how that works. Practically a fair folk tale. A terrible pulp novel where the human in the relationship doesn't really have a choice in the matter since everything will be perfect if they just accept it."

"Oh, no, not perfect at all. First, I am not—ever—gonna push you to turn. It is completely and one hundred percent your choice. It does take some pretty exceptional circumstances for it to not work out even when one half of the pair isn't a vankire—it really is about compatibility, the then-not-an-Empress was a human for a while after the then-not-an-Emperor mated on her, and they worked out very well together then, and there are lots of other examples of vankires mating on hybrids and stuff." Deep breath. "And there are the, erm, cons."

"Which you might want to hold off on listing until we're in a study room," he says, as the elevator opens back to the library's lobby.

He returns the test room key and gets a study room's in exchange.

And once there:

"Two main ones, arguably three if you consider the mating thing a con, I was on the fence about it, arguably four if you consider 'sparkles in the sun' a con, I personally find it awesome. The first is that the turning process consists of three days of terrible agony."

"...Go on."

"I cannot overstate how bad it is. It is really, really bad. As in, it feels like your body is on fire and it never stops, and then it gets worse. It's bad enough most people want to kill themselves while turning, it's bad enough there was a witch back home who could use the memory of pain she'd experienced to induce pain in other people and she could incapacitate vankires with that memory. A human mind would be wiped clean by it, probably."

"But not a vampire mind? ...There are anesthesia potions."

"...if they are magic they might work, but I know what I'd bet on. That witch's twin brother has the power to completely nullify senses and he's the only known way to make it not be incapacitating, anything less than that I'm not sure I'd be even remotely confident in."