The Department of Mysteries, located on Level Nine, is a section of the Ministry of Magic that carries out confidential research involving particular enigmas (death, time, space, thought, and love) and stores copies of prophecies. Most of its operations are carried out in total secrecy from the general wizard populace[12]. However, the primary operations of the department seem to be more like those of scientists, the department attempting to uncover the sources and rules that govern magic.

Few wizards within the Ministry actually know what is located within this department. Those wizards who work in the Department of Mysteries are known as Unspeakables because of the covert nature of their work. The also rarely talk, even to their co-workers.