Harry follows. "So I still have no idea who you are, really. What are you doing here? Why do you cast spells with a sword instead of a wand?"

"I'm a cleric of Iomedae, and I'm afraid I don't really understand what I'm doing here myself", she says wryly. "I got a letter from an archmage--someone like what it sounds like Dumbledore is--that sent me here, and said I'd get sent back when I finished 'the obvious quest'. So I might just vanish again once we're all back somewhere safe, or there might be loose ends that need to get handled first. Or she was lying and I'm stuck here and I'll need to Plane Shift myself back home, but I don't know why she'd lie about it. I was previously in Otari, on the Isle of Kortos, in Avistan, on the planet Golarion. Oh, and I don't cast spells through my sword, I cast them through this." She taps the sunburst-and-sword medallion at her throat.

Huh. "We're in Hogwarts, in Scotland, on planet Earth." Does that make her a space alien like in Doctor Who?

"What's a cleric?" Ron pipes up from the back of the group where Ginny is leaning on him.

That's a weird thing to not know; hopefully she's not somewhere like Rahadoum. Would Nefreti Clepati send a cleric to Rahadoum? . . . Yes.

"Clerics get our magic from the gods, rather than from study or being born with it. Iomedae is the goddess of prioritization and defeating Evil, and I also care about defeating Evil as efficiently as possible, so She gives me magic to help me advance our shared goals."

"Are there other gods of other things?"

"Yes! There are Good gods who help mortals with farming and healing and art and travel and parties, and Neutral gods who do trade and self-improvement and revenge and stuff, or who don't care about mortals at all and just care about the sea or the forests or whatever. And there are Evil gods who suck and cause problems on purpose."

Getting magic from someone else seems worse than just having it. "If you stopped doing what Iomedae wanted, would you lose your magic?"

"If I became Evil, or Chaotic, or a bit of both, or if my priorities changed completely, then yeah," Samora explains with the total lack of anxiety of an astronomer explaining that it would be bad for their health to be suddenly teleported to the surface of Venus.

Yeah, see, that's not as good as having magic you can do whatever you want with. 

"Chaotic?"

Alignment system infodump! With afterlife capsule descriptions!

"I'll believe they have that wherever you came from, but we don't have that here."

"No, you definitely do--or, you might not have the spells for detecting them, and without that or gods I could see not having a formal theory of them, but you definitely still have the thing where people can help each other or hurt each other or be constrained by commitments or not. And my Detect Evil ability still works here." (Harry still reads faintly Evil despite having just risked his life to rescue a kid and defeated some kind of Evil necromancer. Maybe it's something in his pockets; maybe he has some kind of Marshall situation. Not being a skeleton in particular, necessarily, just being some kind of entity that pings Detect Evil no matter what his actual soul is doing.)

"Can you detect any of the other ones, or just evil?"

Tentative handraise?

"Come off it, Gin, there's no way you're evil."

"You're not. Most people your age are True Neutral, but if you were any of the other three I wouldn't be able to tell, Detect Evil is the only one I have on automatically. I could prepare a spell to see the other ones tomorrow, but I generally don't, there are other spells that are more useful and I only get so many a day."

Wow her magic is way worse. No wonder she has a sword all the time. He did not previously have strong opinions on swords but as of today he's pretty in favor. "Why do you get Detect Evil automatically and not the other ones? Did your god pick it?"

"Well, in my case it's a bit complicated, but yes, Iomedae tends to hand out Detect Evil, Evil gods tend to hand out Detect Good, etc, because that's what's most useful for combat. A bunch of my combat spells hit harder on Evil creatures than Neutral ones and don't hurt Good ones at all, and also being able to tell if there's an ambush on the other side of a door is a big help."

"Was the big glowing sphere one you used against the basilisk one of those?"

"Yes. It wasn't very effective because the basilisk wasn't actually Evil. It was a threat to innocent people, and we had to kill it to stop Riddle, but it wasn't Evil. I think it just wasn't smart enough to understand why it shouldn't kill us just because Riddle told it to." 

Harry stops, looking thoughtful. "When you did that second one, I ended up in it by accident, and I thought it was going to burn me like it did Riddle and the basilisk, but it didn't. Does that mean I'm Good?"

She hadn't been sure whether he'd actually gone in or just missed the edge of it, but she doesn't think he's lying. "It would mean that, yes. Which is odd, because you also show up to Detect Evil. I've seen it before, people with some kind of Evil magic attached to them who were themselves Good. You wouldn't happen to be secretly undead, would you?" She smiles to turn the question into a joke. If he is secretly undead and doesn't want to tell her, that's his business.

"Is there a way to tell for sure? The stuff Riddle said to me, about me being like him . . ."