A thieves guild is like any other group of allied people, it just tends to cover all sorts of illegal activities. Often thieves guilds try to gain monopoly over thievery in cities. They also tend to the be the only places where roguish equipment can be bought from.BALADRAS
There is no information about whether such a group exists.
The Group first heard it’s mention when questioning Rick “the Bandit”, who claimed to be a member of it. The only other time was when Rob Samsung mentioned they tried to frame him, a time later said he was part of it but that mentioning it is dangerous.