"That's probable, and since he could not then unsummon the demon..."

Wince. "Then it went and got someone else after him."

"Indeed. And only the original summoner can unsummon it."

"… Can it be killed? Hopefully?"

"Yes, with an iron blade bathed in the blood of its original summoner. It's... quite difficult to get rid of the demon without murdering its host."

"Lovely."

"Quite difficult means it's possible, though, right?"

"Yes, by getting the demon to leave its host for a new victim before its life cycle is complete."

"So we have to find the librarian's body, bathe an iron blade in his blood, get the demon to leave its host to try to grab someone else, and then stab it with this blade." Sigh. "Wonderful."

"Does it only attack humans? As in, would I have any benefit here being probably-about-half-demon?"

"The book doesn't say anything about how it acts around part-humans, those are fairly rare." She glances at Sadde. "Anywhere other than Sunnydale."

"Okay," he says. "Probably not a good bet to assume it won't just kill me, then."

"So, does it kill the victim as soon as it gets into their body, or are they still alive until it leaves them through the face or whatever, or…?"

"It only kills the victim if it leaves them at the end of its life cycle, otherwise it merely causes unreasonable amounts of internal damage."

"Okay, so getting caught by it wouldn't necessarily be the worst thing because we'd probably notice the host acting strangely – does it get access to the host's memories and stuff, too?"

"Yes, but it doesn't know what to do with them without instructions from the summoner."

"Okay, so it might be able to convincingly pretend to be one of us, which is somewhat annoying. Uh, what does it look like, outside a host?"

She turns the book to the appropriate page and shows it to them. It looks... like a very big arthropod with more legs than it ought to have.

"Um, ew."

"Yeah," agrees Eva. "Ew."

"And you can't just kill it with fire or something? Because that'd be really neat if you could. A fire. From very far away."

"Many demons can only be killed by magical means."

"It'd be nice if I were one of those," he sighs. "Or got it on my half-demon thing or whatever. But okay. Blood of the summoner, iron blade, stab it while it's not in someone's body – and get it out of the gym teacher's body somehow – ugh."

"You don't know that you aren't," she points out. "As far as you know, maybe being beheaded's just a minor setback."

"It's possible to attract the demon out of its current host's body if you lead it to believe that your body will be more likely to interact with other bodies..."