Very cool, as usual, but it seems as though it should have an alignment restriction [maybe there is one and I just missed it]. I'm not necessarily saying it needs to be only good or non-evil, though those would fit, something like a requirement that their alignment match that of the mainstream of the city could also work.
I dunno, these guys can be pretty much what they like. Didn't think there was anything in here that hinted towards one leaning or the other.
For some reason it really gave me a Planescape (Torment) vibe. Was that intended?
Though I've heard a lot about Planescape, I don't know much about it.
I think a beguiler might make an interesting base for this as well.