I was going to devleop the Architects and by extension the City from a sort of pseudo-historical/pop culture view of masons/secret societies. So basically the shadowy controllers, but with an underpinning of alchemy to explain why they have access to transhuman tech, and a smattering of ancient astronauts bullshit. Basically a sort of conspiracy theorist approach there, with the Architects being obvious illuminati expies. Alchemy also comes into play wrt the materials found in the City, with allusions to the great work and its components.
The City is basically a nexus of chaotic stuff, and they're not so much in control of it. Parts of the faction- Such as the hitertho unemtneioned Seekers and Gentry- Are deviations from the Architects, with their own pseudo-gnosis to draw from. So basically I am running one big overaching faction with two or four smaller subfactions. They'd have their own heroes, but overall the City p. much presents itself as an united front to the system.
Which it's not. It's rife with internal dissent among the ranks of the Architects, and it's full of dark hungry secrets. Basically a riff on the idea of the "City" as Man's highest achievements and as a sort of monstrous eldrtich thing that takes on a life of it's own+ Alien ecosystem.