A thieves' guild was a guild of organized thieves and rogues. Most major cities in Faerûn, and some smaller ones, had one or more thieves' guilds. Some were powerful enough to hold significant political power, which they often obtained through bribery and intimidation. Most local guilds were short-lived groups that revolved around a particular individual.
Members of thieves' guild often served one of the following roles, which were divided into divisions in larger guilds: assassins, beggars, bounty hunters, burglars, con artists and tricksters, cutpurses and pickpockets, enforcers and thugs, racketeers, scouts and spies, and fences, smugglers, and pirates.
In Waterdeep, the Thieves Guild was led by a subgroup called the Agents of the Overseer, and ultimately reported up to The Overseer
Street gangs and individuals Thieves Guild members paid their dues to The Overseer, or they weren't heard from again.