At the base of a mountain, someone puts a letter and a small paper wrapped parcel into a mailbox.
"It's a little terrible, yeah. But baths are nice. I'll build you one in case you turn out to like them."
He regards the new staircase thoughtfully and murmurs, half to himself, "It should be pretty..."
"... Would it help your design sense if I brought you to the Plane of Shadow to look around for a bit? See what sorts of things are there?"
"Just making sure. Uh, getting there's easier than getting back, we won't pop out on this plane on your mountain. You can probably do all right with that wind thing, but just in case - can you turn yourself insubstantial? You can navigate the Plane of Shadow without it, but everything shadows build isn't built to accommodate it."
"I can turn into wind, fire, water, and lightning, but I can't do 'completely insubstantial'. Should I build a spell for it before we go? What does being insubstantial look like?"
Saskia demonstrates! She goes from mostly opaque to mostly transparent, a faint hint of Saskia-shaped darkness. Demonstrably, she waves a hand through a wall.
"like this."
"Depends on how long it takes you to build a spell for it. It'll be inconvenient but isn't necessary, you'll just miss out on being able to go indoors in some places. There are still some indoors places you'll be able to see, just not all of them. Whichever you prefer's fine."
"...are there really places that air can't get in and out of? And I can go through windows usually, and sometimes walls if they're thin enough."
"Windows aren't so much a thing in the buildings I'm talking about. No reason, there's no sun, everyone can be incorporeal, and the view mostly isn't. You can probably figure out a way into a place as air if you try, but it might be more a bit more of a hassle thank you're thinking, things are a little..." he considers phrasing. "The Plane of Shadow moves. Mostly the geography, but buildings too, sometimes. The buildings stay still by being built out of things that are very sturdy. Nobody would be accounting for getting air anywhere in particular, because nobody needs to breathe. And that thing that dirt does, where it wants to stay on the ground? Air kind of does it too, it doesn't try to find holes in things like it does on material planes. It doesn't push. So there are a number of factors here that don't lend themselves well to getting places as air. Possibly you could overcome them, but I'm not going to guarantee it."
"Hm," he says. "Is there any reason I shouldn't just - temporarily turn into a shadowperson?"
"It's easier to turn into one than to stop. It happens naturally to people if they stay in the Plane of Shadow for long enough, actually. If you could magically make sure you can turn back, then no, it'd likely be useful. You'll be more vulnerable to light and certain kinds of holy magic, but those won't be much of an issue if you can switch between forms."
"Very few things are irreversible when you're me! Let's see how long it'd take to build—"
He pulls a bit of power and tells it what he wants. Veron is right, it is easier to do it than undo it, but building a spell that switches him back and forth still looks much easier than he was expecting. "Huh, not that long," he comments. "Probably less than an hour, especially with the mind artifacts. If that's longer than you'd rather wait, I can skip it for now, though."
"Yes," he says, smiling adoringly at Saskia, "you can absolutely read in my library. If you feel like wandering around, you can do that too, but please stay out of the northwest wing; it belongs to my daughter."
"... If you'll be busy for a while, is it all right if I check on your other guests? With you and with them, I would rather not scare anyone."