Hi, Chelsie. I am Dora, the cranky old (not-)man of Gates, and oh ho ho I am looking forward to Cyril shenanigans. So, my roster at the moment, for your purview:
Emily Andley (wordsaremusic), the Natural-born polyglot who is fluent in basically all language ever, including of the unspoken body sort, and is Gates' Mary Sue if you can just forgive how extraordinarily fucked up she is. She's a couple of years older than Cyril, and although her father is a Librarian, she has no love lost for the organization. (Despite being, magically, a bit of a shoe-in to work for them.) Since dropping out of university, she's taken to living and working full-time at the aforementioned Haven, and is the more personable half of the people who keep it running. Most of the time, at any rate. She tends to stick her nose where it's not needed, and has done fantastically stupid things like strike up a deal with London Market's head Merchant, so gosh I would like to throw her at Cyril sometimes since it sounds like they're both floundering a bit in the wide world.
John Constantine (conjob), the Occultist who hardly seems to use magic, is addicted to it anyway, and tends to piss off everyone ever by a) existing, and b) being a complete and utter dick to all and sundry. The Library doubtless has a file on him which spans volumes. John's cool with this. John, despite really enjoying the act of wallowing in his own purple-prosed misery, is also largely laid back and will cheerfully give Cyril shit on general principle. He likes Librarian trainees; they're at that stage where they are not yet bereft of all personality.
Elizabeth Gryffiths (outofboundaries), token mundane and one of the already-mentioned many Gryffiths sisters (she is number seven, I believe). Journalist by trade, really bad single mom by accident -- it's for the best that her son spends most of his time with his father -- and recent inductee to the magical world. It's weird, it's creepy, it is fucking terrifying. She loves it. The Library as a concept and an institution fascinates her, and as her favorite baby sister is on par with Cyril in the Librarian food chain... well, she will likely take interest enough to ask plenty of questions. Because it is what she does.
Julia Rayne (borrowedthings), Occultist who is exceptionally talented at all but surgically removing bits of other magicians' magic for her own keeping and use. She is extremely subtle about it. Half the people she 'borrows' magic from don't even notice the act of taking. Julia's fairly ambivalent about the Library, but she would be somewhat known by them, particularly any Librarians who have a focus on the Market. She married into the Market family by way of Nic Santoro, and while they're divorced these days, she's still a known fixture of sorts. Her family also acts as middlemen between people who supply raw magical materials and the Market Vendors who sell finished product, so there's a bit of law-skirting which the Raynes might also be known for.
I also have Vaughn Wagner (playingdoctor), who is a fairly miserable and unpleasant healer at Haven, and Liam Ward, who has been running a gang of mundane and magical conmen for the last few years, for what it's worth. Anyway, a bajillion characters later: welcome to Gates, v pleased to have you here!