In every city in Avengail there are rumors of a Thieves Guild. Of course no one knows who runs them, or where they are located, but the rumors persist. they tell of the rigors it takes to join them and of the punishments they deal out to thieving non-guild members.
Joining a Thieves guild can be as simple as running the thieves maze, or as complex as a multi part initiation ceremony. The leaders of these guild run them with an iron fist, and deal out harsh punishments to rule breakers and offending non-guild thieves.