"And here I thought you were just an extremely gifted witch. . . . You don't look like a crab. I suppose you did look a bit like a star, earlier."

"Oh, this isn't my natural form, but that wouldn't fit indoors. I figured out how to look like a human and not like a giant diamond crab when I was eighteen. The transformation doesn't quite go all the way, my bones stay diamond," she opens her mouth and sticks a finger behind her teeth to demonstrate their transparency, "and I don't have any of your sort of magic at all. Just star magic and space crab magic."

"Fascinating. I've heard of wizards hybridizing with magical creatures before, but the offspring are generally wizards as well. And, pardon me if this is indelicate, but how does one hybridize with a star?"

"Please. I'm not even a regular masochist, let alone the hardcore emotional kind of masochist it would take to ask my grandparents how they had sex. But it's probably relevant that my parents are a human and a star/crab hybrid, I don't think a human could survive being close enough to a whole Judgment to produce offspring. I could be wrong, though, if they were protected...anyway. My father is just a giant glowing mountain, not a star, and no I don't know how that worked either."

Binns has the grace to look extremely uncomfortable. "I apologize for my rudeness. Did you want to learn more about recent history?"

"Yes please." 

Okay, post-Grindelwald British wizarding history, much less unpleasant than thinking about getting raised from the dead by a part-human! Muggles got potentially world-destroying weapons and also got a lot more numerous, which made all the magical governments very nervous. Britain in particular also had to deal with the rise of He Who Must Not Be Named, another dark wizard who wasn't as good at building a power base as Grindelwald but was a lot more unhinged, to the point where there might not have been any British wizards left to conquer if the war had gone on much longer. Then You-Know-Who was defeated, some say killed, by a one-year-old baby, Harry Potter, who's actually old enough to be attending Hogwarts right now. "Why, I probably have him in my classes. I stopped keeping track a long time ago, it didn't seem to matter who was in the classes because I would give the same lecture regardless."

"Being dead is bad for your health. Thank you for explaining. Do you know where I can find other ghosts?"

"Well, there are another four in this castle, but I don't know where any others live."

"It's a big castle, and I'm new here."

"The house ghosts mainly spend time near their house common rooms--but I suppose you wouldn't know where those are. What brings you to Hogwarts, anyway?"

"Oh, I fell down a magic well and randomly appeared on a field where some children were playing some kind of game on broomsticks. And then these horrible things in cloaks showed up and they must've been death-based in some way because my healing light destroyed them."

"How odd. Well, I hope you find Hogwarts hospitable as long as you're here. I'd offer to help you find your way to one of the other ghosts' common haunts, but, ah, I'm afraid I don't remember much besides how to get from here to my classroom and back. That's going to be rather bothersome when it gets to be suppertime. Ah, well, we shall both have to emulate the first years and ask the portraits for directions."

"Ask the--hm. Alright. How does that work exactly? The portraits, I mean."

"They're sort of, recordings of a wizard? They remember most of what the wizard remembered when they were painted. They can see out of their frames, and move into adjacent ones, so they get to know their way around.

"So there's a sort of parallel area behind the frames, that the portraits can move around in?"

"I'm not entirely sure; you might want to ask a portrait about it. I know if one person gets painted multiple times there ends up being only one and they can move between those frames at any distance."

"I will ask a portrait about it. Thanks."

"You're welcome. And thank you again for the, ah, resurrection. I'm going to need to revise my lesson plans, they've gone rather out of date, but do feel free to stop by any time I'm not teaching a class."

"I will!" 

She leaves the classroom and looks around for a painting.

There are several paintings in the area! She can talk to a stern-looking old witch drinking tea, or a group of three wizards playing cards, or a witch in a blue dress picking flowers.

"Hi!" she says to the flower witch. "Where I'm from paintings aren't alive and I'm curious how that works."

"Hi! I'm Mildred. I don't know how paintings work exactly, but I know a wizard has to paint them and I'm pretty sure the canvas gets soaked in a potion either before or after. Maybe both."

"That is good to know but it's not what I meant, I was more curious what it's like on the other side of the canvas."

"Oh! Silly me. Hmm. Well, it's always sunny, at least in this frame. And if I don't want to talk to anyone I can just walk off into the background for a while. And things don't change much. It's very . . . calm. Peaceful."