She is only allowed to fly to her destination, not anywhere else. She notices that she is not where she should be, that she cannot progress to where she was told to go, and she careens out of control when her wings won't flap anymore, and she crashes.
"...I think I will answer that question with pretty pictures," he says. "First—" A holographic model of a solar system appears. "Do I need to explain planets?"
There are a lot of tiny sparkles. He enlarges the display until it fills the vid plate's entire active area, and there are still some places where the tiny lights cluster into an undifferentiated glowing mass.
Promise looks at the galaxy. "That's a lot of planets," she says. "Why is it organized like that?"
"Gravity?" he hazards. "I'm not a physicist. I can probably find you anywhere between an article and a few dozen books on the subject, depending on the exact depth of your curiosity."
"Fairyland isn't like that," she says. "It's just flat. With mountains and caves and things, but basically flat."
"Well, the mortal world is... sparkly," he says, smiling. "...Also, we have some difficulty transporting mortals between these various locations, and depending on how exactly your gates work, if you could create or teach someone to create a stable network of instantaneous interstellar transportation I don't think it's possible to overstate how rich you could get. Sending you home with the entire collected works of humanity, or at least as much of it as I can reach from my living room, would be cheap. What you could get for a gate network... I struggle to even describe it. You could buy your own planet. You could pay hundreds of people exorbitant salaries to comb the galaxy looking for the nicest previously unclaimed planet available and then declare it yours and settle down there with your library of all human knowledge."
"That might be nice. And I shouldn't necessarily go back to my tree very soon anyway. In case someone's looking for me. It'd be the obvious place I'd go."
"When you say 'your tree'..." he says, trying to think of a way to formulate the question.
"The kind of fairy I am starts inside of a tree. I lived there, before. I'd only be going to take a cutting to plant a new one, but that could be long enough even if I went with my eardrums burst."
"...Long enough for someone to - recapture you? What's - I mean - depending on the exact nature of the danger involved, that may be a problem that I and/or an arbitrarily large pile of money could help solve."
"My old master collects sorcerers and most of them are better than me and the tree's my turf, which matters, but I haven't been there in such a long time and I don't remember all the things I'd need to know to press the advantage. If my ears were broken someone would just have to heal me, that's all, and get out an order before I could puncture them again."
"What if you were, for example, wearing something that blocked your hearing without damaging you...?"
"They'd just have to wreck it. Maybe it'd be safe to open a tiny gate, just big enough for my hand and a branch..."
"I would be happy to offer you any reasonable assistance in getting a cutting of your tree, if it's that important to you," he says. "And varying levels of extravagant assistance are potentially on offer if you decide to do things like teach me sorcery or sell gates. Although the logistics of selling gates could get... a bit complicated."
"...I need to spend a minute thinking this through, actually," he says, and sits down at the desk.
Promise makes more harmonic maps of other locations, meanwhile, confirming that they are Yep, Super Flat.
If there's a magical immortal fairy from another world in his living room with the ability to command anyone whose name she knows, he has to tell Illyan. The security implications are staggering. It only takes one syllable. 'Vor' is a syllable. She could conquer the planet. She probably couldn't keep the planet, but she could conquer it.
Illyan is going to think of this situation in terms of threat (huge) and advantage (also huge). He doesn't normally make policy decisions solo, but on something like this... he might end up giving Miles an order which Miles would have to desert the Imperial Service over.
And just why would you desert the Imperial Service over this, Silver?
...Because she is his vassal. Actually, if she hadn't used that word it probably would have taken him a lot longer to figure out why he feels this sense of responsibility toward her. She didn't sign up to be a Barrayaran resource. She was in a bad situation and she did what she had to to get out of it, and now here he is with his very own irrevocably magically commanded fairy and his Barrayaran soul looks at this and says, I pledge you the protection of a liege lord.
If she becomes the richest person in the galaxy by selling impossible dimensional doors, Illyan's going to notice, and if Miles has been orchestrating it under his nose, Miles will be in the deepest of shit.
She's going to need an intermediary if she wants to deal with the number of humans she'd have to interact with to sell a gate network, because even if she doesn't have ethical qualms about learning a million names, Miles does, and ethical qualms aside, if the wrong person gets an inkling that they are under her irrevocable magical command they could end up putting her immortality to the test. Among other potential unpleasant reactions.
If he went to Gregor rather than Illyan... well, Gregor would like to buy an impossible dimensional door or two, Miles is sure. And Gregor would not like to put Miles in a position of conflicted loyalties. Gregor of all people should understand. Illyan might complain, but Gregor can shut him up.
Okay. So he has to figure out some way to explain all this to her, and then he can ask her how she would like to proceed.
(Except - to what degree should he even be trusting her? This is all so far outside his experience... his gut says she's not trying to fool him, the explanations she's been giving have all fit the observable facts, but should he be trying to verify? How? He's not sure there can exist a way to verify the orders thing that is simultaneously ethical and effective.)
Well, for now he hasn't really done anything that would be nonstrategic if this were all an elaborate hoax. But he should think of a better verification for at least the sorcery part if he's going to go to Gregor over this.
He breaks out of his thoughts and looks around for Promise.
"Harmonics are an invisible feature of places," Promise says. "They vary, usually continuously but not always and at various rates. Sort of like... ground level. Except in three dimensions. They're one of the things that matters for sorcery, and when they are all the same it's a lot easier to take them into account. I don't know why mortals wouldn't already have sorcery if it's flat everywhere. Maybe it's only flat some places."
"Or maybe sorcery can only be done by a fairy, or in the presence of a fairy, or only learned likewise, or maybe there's some less guessable connection to the very weird fact that fairies have all heard of a mortal world where they think sorcery doesn't work but this mortal world, where sorcery does work, has only heard of fairies as fictional beings with some of their most relevant properties omitted. It's fascinating and I'm fascinated but before I get too far into that, I want to talk to you about your immediate plans. How much interest do you have in becoming unspeakably rich via the sale of interstellar portals?"
"I... kind of want to spend at least a month living an extremely boring life in my own tree putting my psyche back together. But after that it sounds more interesting than most things I might be doing in Fairyland."