Here is a bar. At it is a girl, late teens - ? - dressed in wide bands of black silk tied ragged edge to ragged edge in a neat pattern. There's a small owl on her shoulder and a stack of napkins at her elbow and she's nursing a cup of something steaming and spicy.
"I make jokes, occasionally. It's a hobby. There's no soul harvesting clause."
"Hi!" says a voice from the vicinity of the cat. (The cat himself does not open his mouth.) It sounds enthusiastic, and not very much like an ancient artefact of dark wisdom.
"Hello, not-currently-skull. Am I going to overtax your interest in arcana if I hang out asking you questions and taking notes all day long most days for a very long time?"
"...Have you met a spirit before?" the being asks incredulously. "Interest in arcana is literally the purpose of my existence. Everything else is background noise."
"It seems polite to ask first. Hi, I'm Bella and I will be your nerd for the foreseeable future."
She has a notebook - she has several, actually, but the questions and what she has so far are in one and the others are for storing Bob's answers.
Seems like she's really curious about changelings.
They are eventually shooed into a different bit of the room due to the existence of another client, who needs her pearls found. David charms her outrageously, receives an advance, and puts on his coat. Before leaving, he turns to them.
"Should be done shortly. Don't go anywhere, the omniscient magical database is all well and good but I like that cat."
"Okay. I really don't think the Misters Dresden would like it very much, so if you're having fun you won't blab. So, I'm not a changeling. And that's my problem."
"I would like," says Bella, "to be a changeling. Technically. Without interfering with my parents in any way that might inconvenience them."
Bob hums. "I really, really want to make some kind of tasteless joke about joining the winning team, but it sounds very evil, so I'll refrain. But. I begin to see why you wanted my help."
"Yeah, I might have tried the Archive but she's likely to be busy on other matters, likely to disapprove, and also I wrote her a stern letter when I was eight."
"Busy on other matters, like I said. Anyway. I want to be rid of my baggage, and I want to hack the process for valuable prizes on top of that, and I want to turn out with exactly the right specs in the brain after the fact - I can specify that better than the average bear, but zero tolerance on turning up with a thirst for blood or an obsession with shoes, I don't have time for that crap. Can you help me?"
"Are you willing to spend a decade or so meticulously constructing a metaphysical artifact half a dozen orders of magnitude more complex than those bangles you're wearing, while suffering through both my dubious company and that of Heckle and Jeckle Dresden, in exchange for giving up the barbell that keeps you at the bottom of the supernatural totem pole?"