Palladium never really touched on this, though they have given prices for the various services that the guilds perform, they never touched on the guild's structure. Granted, there is no universal organization of thieves' guilds, the organization and even frequency will vary with the country or region of the continent. For instance, the thieves guilds of the Western Empire will be different from those found in the Land of the South Winds, Timiro Kingdom and the Domain of Man in structure, organization, influence, and membership. What follows is information on the thieves' guilds by country.
Note: Because of the sheer size of this article, I have decided to do this article as a series. As I learn more about a region/country/nation, I'll post information on those guilds.
The Western Empire is home to the most vicious thieving guilds. The guilds hold great political influence as each regional lord seeks their help in "eliminating" the competition. Guilds of every region have their hands in at least one political scheme, usually more. Due to the people in the Empire being either incredibly wealthy or incredibly poor, the thieves' guilds have a large number of members. Each guild holds various territories with in a city. Certain streets are "owned" by a guild with the guild being in constant competition with other guilds over territory.
As few as five and as many as twenty guilds exist in any one city, depending on the city's size and population. Thief guilds are very structured, with one person running the guild and making all the decisions. This person is known as the al-Sahid of the guild. Each al-Sahid has from three to five lieutenants who act as enforcers and bodyguards. An al-Sahid is a thief who began at the bottom of the hierarchy and worked his way up, by proving his or her worth or killing a higher ranking thief or assassin. A typical hierarchy is as follows: Apprentice, Enforcer, Informant, Spy, Assassin, Lieutenant, al-Sahid.
An Apprentice is a thief who has just joined the guild and has yet to prove himself. They are typically given assignments such as enforcing petty slights to the guild, including peasants not paying for "protection" and other extortion. Apprentices are typically sent after only peasants, never against other guilds. They are typically first to second level.
Enforcers are thieves who have been in the guilds for at least two years and have proven themselves (third to fifth) loyal to the guild. Enforcers are sent on assignments of extortion and retribution. This can involve anything from public humiliation to a beating. Occasionally, if a thief tries to leave or double-crosses the guild, an Enforcer is sent to "warn" the individual.
Informants are different from Spies only in the fact that they are never sent to infiltrate other guilds. Informants are limited to gathering information on the streets and, in some cases, from noble houses, have been members of a guild for at least four years, and are fifth to eighth level.
Assassins are skilled killers who have proven themselves quite capable with weapons. Though the instruments differ from bow to sword to dagger, the end result is always the same. An Assassin has proven him- or herself an invaluable resource to the guild and commands a high price for their services. Assassins are used when a guild wishes to make a statement and are usually involved in political assassination, plots and treachery. Assassins have been guild members for at least five years and are usually sixth to tenth level.
The Lieutenants are people recruited from the ranks of Informant, Spy, and Assassin who have caught the eye of the al-Sahid themselves. They act as personal bodyguards for the al-Sahid and enforce his "laws" within the guild.
Western Empire guilds are some of the most powerful in the world and are also the most treacherous. The general alignment of thieves in Western guilds range from Anarchist to Aberrant. Though Aberrant is rare, with Miscreant being the most common.