"You know," Last-Falling-Winter-Leaf says, voice trembling ever so slightly, "how there is a, a loop, of the substance of water? From cloud to rain to river to sea to sun-warmed vapour to cloud? And there are such cycles, too, of magic. That's the nestled seed of truth within the superstitions about witches and running water, yes? A crudely constructed cthonic mana effect will have its power rapidly thieved by the boundary effects with any naturally open hydroic sink, because water is — is hungrier."
"Mhm," Tili says, watching the elf with sparkling human eyes.
"And elves naturally respirate a lot of mana, so we have anatomy for — humour balancing."
"Mhm," Tili says, drawing it out.
"So it's not a p-penis," Last-Falling-Winter-Leaf says, wishing the blush on their face wasn't quite so obvious. "It's a manadynamic vane. Like the eartips. It's for, for when you accumulate too much cthonic charge through ground contact, it bleeds it into pnoiac mana, yes?"
"Mhm," Tili says, and runs the blunt end of a pencil thoughtfully across a glistening bottom lip. "But can you fuck with it?"
"Tili!" Last-Falling-Winter-Leaf looks frantically around the university library's reading room. "That's not a question that's — you can't simply — I wouldn't ask you if humans use any given body part to...."
"Yes," Tili says. "You and I both know, if humans have a body part, and they could use it to fuck, we do."
"It's not for—" Last-Falling-Winter-Leaf squirms. "If. Maybe. Perverts."
"Oh, dirty sex," Tili says in a warm, purring, altogether-too-amused-at-the-elf's-expense way, gaze dropping to the front of Last-Falling-Winter-Leaf's britches.
"It's not even what you'd properly call erectile," Last-Falling-Winter-Leaf whines. "It's a mana vane, it only even — stays up when there's pnoiac mana dissipating through it—"
"Oh," Tili says, with sudden terrible interest. "It's an air wand," and taps the pencil slowly and thoughtfully against a newly pursed mouth. "So if you put the right charm on it," Last-Falling-Winter-Leaf's fellow student continues, in a thoughtful yet suddenly somewhat distracted way, "you could put it down somebody's throat all day with no concern for their breathing—"
"Will it satisfy your curiosities in some other way than asking me if I tell you how to locate, within the library, all their classical elven smut," Last-Falling-Winter-Leaf says desperately.
"That would be fascinating," Tili says, and waggles an eyebrow. "Though if we're speculating on sating me in other ways than talking about it...."