Thieves Guild is one of 4 major guilds in Elder Scrolls Online. It is a large legendary organization of thieves, adventurers and professional enterprising operators with a huge network of shelters and bases all over the continent. It is dedicated to training or gathering of those who are stealthy and shadowy in nature. Unlike Fighters Guild, Thieves Guild is illegal.
How this organization could survive for so many years? The government considers it as "crime regulator" because it does not tolerate competition or egregious conduct from its members. There is a list of special rules that every thief must obey. Though most of the members have bad reputation, law of the guild does not allow them to rob each other and kill other people. So the government thinks that it is better to have a regulated criminal organization instead of criminal anarchy.
The guild consists of many thieves, burglars, smugglers, pickpockets and other people who have chosen shady criminal life. Organization is always open for new members who are stealthy, sly and who wish to enter the guild. Doesn’t matter what race or faction you belong to.
Members of the faction specialize in stealing different objects from different places and loaning money. Very often the guild is asked to find and steal definite thing for the reward. All members are great thieves and masters of sneaky movements. That’s why all victims understand that they were robbed too late. The guild consists of different specialists who can unlock doors, move without being detected and so on. But there are not only true criminals there. There are also many adventurers who like to explore ancient dungeons in order to find something valuable.
People do not like the organization and view them unfavorably. Most of the people do not feud with the guild because they afraid the retribution. That’s why the guild has shelters or safe-houses in most of the largest cities in Tamriel. Safe-house is a place where the guild is based. Each member can sell stolen things and buy necessary equipment there.
All members of the Thieves Guild believe that Daedric Princess Nocturnal is patron of their brotherhood. They think that she protects the guild and helps members to succeed and not to be caught.