"How does it do that?"

"I'm not sure what kind of 'how' you mean - for devising one for oomph I'm going to design what I want oomph to look like, since it's not in discrete units like wizarding power I'm probably going to go with a metaphorical substance in a metaphorical graduated cylinder, and then while I have that spell on, if I look at a unicorn I will be able to literally see this cylinder however full it is. I'm probably going to use you as a baseline because I've met you, with enough leeway that if you suddenly doubled in oomph the spell would handle it - I'd make a new version if I needed to handle ranges bigger than that."

"Yes, that's what I wanted to know - how it presents the information. If it matters to your spell, unicorn magic comes in colours - every unicorn has a specific colour that their horn glows when they're doing magic. My horn doesn't usually glow, but when it does it looks like this." She concentrates for a moment and a pale blue glowing aura appears around her horn; it doesn't quite just emit light, because if that was all, the colour wouldn't be so clear. "So if you made your substance look like the glow, you'd get a little bit of extra information about what the unicorn's magic looked like. The colour doesn't make any practical difference, but it seems tidy to show it anyway."

"Why is it that your horn doesn't usually glow?" Kaylo wonders. "But yes, that's good to know, it can look like a cylinder full of glow."

"It's just a trick I can do. I think it's probably related to my special talent, because I haven't heard of anypony else being able to do it, but I don't have my cutie mark yet so I don't know for sure."

"Huh. When-ish do ponies usually get those?"

"When they're older than me but not a lot older. I'm six; ponies usually get their cutie marks between eight and ten."

"But you still have functional talents before then?"

"Well, it's usually hard to tell. Most ponies get their cutie mark the first time they realize what their talent is, and especially if it's a magic talent and not something like being good at chess, there's no good way to tell the difference between not being able to do it beforehand and just not having done it yet. Maybe if I was an ordinary pony I wouldn't have found out I could make my horn not glow until I was eight, but here I am doing lots of magic before then."

"Huh. Are there any cases of somepony as young as you getting a cutie mark?"

"Not that I know of. But it could've happened a few times and just not been noticed by anypony who would've written it down."

"It's almost like people don't care about researchers having access to statistics. Well, I suppose it'll be informative if you wake up with one on the morning of your birthday."

She giggles. "Yes."

"How long are you planning to stay today?" asks Kaylo.

"At least a few hours, unless your sunset is soon."

"Sunset's in -" He casts a spell, he peers at the time. "Two angles, why?"

"I guess it might be different here - in Ponyville most things start to close a little after sunset when it starts getting properly dark, and I'd be allowed to stay at the library but people who didn't know the librarian well would be asked to go home."

"Library's open all night to students and authorized guests. Aar Kithen watched me summon you, I'd say you're authorized."

"Well, that's convenient."

"Yup. Something like twenty-five percent of why I haven't graduated yet."

"And what are the other three quarters?"

"Nowhere else obvious to go until I'm old enough to claim my pseudonym, and pissing off my aunt."

"Do you have an unpleasant aunt?"

"Yeah, we haven't ever really gotten along."

"Unpleasant aunts are no fun," says Blueberry. "Clover had one of those. Then she went away."