"From their point of view, it would stay as false as if everyone agreed you were six feet tall. Practitioners aren't likely to stick their necks out that way. You could get most of the same benefit if people agree to treat you as your preferred gender, or people acknowledging that what you mean by gender isn't what the spirits mean.

You will find the spirits more malleable around your demesne than other places. Can't expand very fast, but it's better than nothing."

"Hmm. And I expect other practitioners would come to the same conclusion you did as fast as you did, and that'd be a knife hanging over my head whenever I presented as a boy and dealt with them, or Others who were likely to want to duck me over."

"Yes. Good call on the not swearing, by the way.

The extreme option would be to deal with practitioners or Others only while presenting as a woman, if that's the safe gender, but some won't know to connect the identities. Or won't care. Or, for the less sentient Others, wouldn't be able to call you on it if they did."

"...I already used to do the not swearing part, why is it a good call?"

"Partly because it's often too similar to hyperbole, and partly because the spirits are very literal. Not completely, but very. Practitioners can still swear, but it involves taking a minor risk at times when you're presumably not watching your words very carefully. Many get in the habit of cutting back."

"Well, I suppose I have at least one advantage, then," she sighs.

"That, and you don't have to learn magic by trial and error. Most practitioners don't, but most of the ones who don't get born to it do have trouble there.

Case in point: glamour is rare among humans, but I do have supplies for some. Would you like to try it?"

"Really? Yes! I—" Pause. Squint. "Why are you helping me?"

"A couple reasons. Partly because while I have a lot of contacts among Others, I have almost no practitioner allies and am not likely to make a good impression even after going public. The other reason is because of the Seal. It might be a long shot, but it's taking aim at the same target I am.

Still, glamour is hard for most humans to get. Probably shouldn't be free. In exchange would you promise an honest effort to help keep my presence hidden?"

"Well, of—" Another pause. "Hidden from whom or what? What are the qualifiers of that promise? Just how much of a lawyer should I be with these spirits and honesty policy?"

"They expect keeping both the spirit and the letter of promises, but the letter is always enough. It's safer to not have to, but if you're stuck with a promise you don't like you can act as much like a lawyer as you like. Just keep in mind there might be the equivalent of a prosecutor.

In this case, the secret is from practitioners in general until I'm ready to appear out of apparently nowhere. It has been a few years so far, and will probably be a few more. But there's no obvious way to tell which local Others would pass the information on, and of course informing non-practitioners would be dangerous anyway, so it boils down to fairly strict secrecy."

"My thing with these strict promises is that I can't help but imagine the edge cases and exceptions, being caught between a rock and a hard place, like someone torturing me for whatever reason and, sure, if I'm keeping you a secret then there's no reason for anyone to even suspect I might know something, barring some implausible steps of inference involving where I got my knowledge, but."

"Good to know you're wary of promises.
Edge cases are why I'm asking for an honest effort. Not your best effort; that risks forcing you to throw everything else away for slightly more secrecy. If you get coerced or tricked you'd be free to say you tried, and if there's some unforeseeable emergency where you have to reveal me to someone, you'd just have to look for other solutions first.

I'm being vague enough that it leaves a lot of latitude; if you were hostile this would have to be more complex."

"Well I'd do that anyway." She clears her throat and declares, "In exchange for the aforementioned supplies for glamour and some instruction on how to use them, I do solemnly promise an honest effort to help keep your presence hidden from Others and practitioners I meet, unless explicitly and unambiguously indicated otherwise by yourself, until such time as you find it convenient to make yourself known or to release me from this oath." She's clearly having a lot of fun with this.

She could accept deals just by saying yes, she's seen it happen, but there's no rule against fun.

A glass flask stoppered with a cork floats obligingly over. It contains what looks like blood, though it's a bit too dark.
"The first thing to know about glamour is that it's more about how you treat it than what you use it for. You have to regularly think about it, but never as something merely routine, or it will take the chance to slip and become something ordinary. You can grow it, with attention. This is more blood than the faerie I got it from would have given, but even though all of it is his blood it didn't all come from him.

What glamour does can be either one expenditure for a dramatic effect or an ongoing draw. Since you wanted it for its appearance altering effects, that'll be the second type and very intuitive. You can mix it in with makeup, or just put it on yourself directly. There's none of the mundane health or even disgust problems that blood might normally have. Once it's on you, face for appearance or throat for voice, you'll find you can mold yourself. It'll take concentration, and whether it's comfortable can vary, but you can look like anything in minutes. If you're using it to decieve practitioners, use the Sight. What people see in the spirit world when they look at you directly will follow the glamour you apply in the material one, but there's more to see than just appearance. Draw a line with the blood across a connection to break it, and along one to strengthen or mold it. 

That does make it more complex and adds more differences from your natural state.  Those increase the power it will take and the fragility. That's also why you should avoid layering one glamour on top of another, or turning yourself into anything people will stare at too closely. It'll multiply the number of twists and turns you're forcing reality through.

When you use glamour, it'll feel like you have absolute morphological freedom to choose any form. Don't. Always leave something that you'll notice and that will remind you of yourself. Some illusionists always keep the same eye color, or do a working so that their tongue will betray them if they start thinking of themselves by a name other than their own. Physical characteristics are easier and require nothing but the glamour.

If the glamour breaks, if too many people wear it down with too much doubt, reality will reassert itself all at once. That's painful and costs power, both from you and from the glamour, and can also damage your identity. It's not unheard of to be indefinitely stuck with hybrid characteristics of whatever the glamour was, and you wouldn't even be able to choose which ones. To take th glamour off, you just wash it off while intending to get rid of it. Glamour is cooperative about interpretation."

"The kind of thing I'd use it for would be only, you know, physical sex changes, most of the time, probably. I'm not even sure what kinds of relations and connections I'd have to alter to change that, if any, it's just." She shrugs. "Anyway, how do you make it grow? Is it just... paying attention to the blood? Pet it, give it a name, talk to it?"

"There are probably a lot of ways. Glamour is a very subjective kind of magic. What I did was dilute it with ordinary blood—about as ordinary as blood ever is; it was forcibly taken not freely given, and from animals—and let the glamour expand to charge the wider area, then repeat. Slow process, but effective. You can grow it less slowly than I did by keeping it with you, maybe putting the container in a pocket you often find your hand in so you feel it. Regularly noticing and handling it helps, but don't let it become routine. It will take the chance to fade into the background and become no more than what it looks like. For the same reason you should make sure not to dilute it very much, if you do that; I kept it above nine parts in ten.

Naming it could help. I never thought of that one. It actively tries to be temporary as much as any inanimate object ever does, and what stops it is that you'd be thinking of it as something special."

"Hmm, I'm not sure I can carry a flask of blood around and look at it all the time, especially if I want to be secret from people, especially other practitioners."

"It'll be slower if you don't, but that's up to you. Are you planning to try to be secret? Most practitioners and some Others will be able to tell by looking."

"I'm not sure, yet. The Duchamp and Behaim kids know about the gender thing already."

"And if you suddenly get much better at appearing how you want, someone might take a second to check for magic and see you've awakened. You might be better off just walking into a council meeting and introducing yourself."

"...council meeting?"

"I haven't mentioned those, have I. Monthly meetings where practitioners and sentient Others talk about whatever minutiae affect other council members or the balance of power in the town. For a new practitioner it would be polite to let them know you're here, but deciding not to shouldn't earn you any real enemies."

"Hmm, I wonder what's worse, having those snobs figure me out on their own or introducing." Pause. "I think I'm gonna introduce."

"And this way we have time to come up with a cover story for how you awakened. We can arrange enough details to be true to support a plausible narrative, but somehow I doubt many people would believe there's nothing more to it if you say you stumbled across a copy of Essentials in an abandoned house."