Thieves' guilds are organized groups of criminals that specialize in theft and other illicit activities. They often operate in secret, establishing rules and codes of conduct among their members. These guilds can provide protection, training, and resources for thieves, allowing them to work together more effectively and avoid capture by law enforcement. Historically, thieves' guilds have existed in various cultures, often forming in urban areas where crime was prevalent. They may engage in activities such as burglary, pickpocketing, and smuggling. Some guilds even have a hierarchical structure, with leaders who oversee operations and manage disputes among members.