Dyvers doesn’t have a thieves guild like the city of Greyhawk, instead they have a gang known as the Alliance. According to Slavers, the Alliance was formed by several competing crime families so that they could take out their rivals together. This feels more like a mafia thing than a gang, and if that’s how you would like to play them you’re more than welcome to do so.
I, however, tend to treat them like they’re a bunch of different street gangs that have come together with various levels of aptitude. There are some who are capable of running legitimate businesses that they use as fronts for their criminal activities (like the woman above), and then there are others that paint their faces like jackals and laugh as they mug people. I want it to feel like there are dozens of these gangs moving about, competing with each other, but at the same time connected.