I wanted to make sure the mythology of the series was rooted in world mythology — not just Western religious mythology, though there is a lot of that, given the books’ partial basing on Paradise Lost and The Inferno — so I did a lot of reading up on world mythology, especially anything having to do with good and evil spirits. I wanted to make sure multiple types of demonic myth were present, so you’ll find Japanese, Indian, Tibetan, and other kinds of demons represented (plus the kind I’ve made up.) I read a lot of old “demonologies” — there was a whole time period where scholars were obsessed with listing every kind of demon and mapping Hell. I read up on the mythology of angels and fallen angels. Raziel, for instance, is an angel from the Jewish kabbalistic tradition, who is supposed to have given Adam, in the Garden of Eden, a book of wisdom — he is sometimes called the Angel of Secrets, or Angel of Knowledge. Therefore he seemed the right angel to have given the Gray Book to the first Shadowhunter. Nephilim in mythology are the “offspring” of men an angels, so that’s obviously a myth I adapted a little more freely to make it serve my purposes. And so forth.