A Quaestor is an official of an archmage's Sconce in the magico-legal system, responsible for the conduct of investigations into possible violations of magical law or regulations. In most sconces, the Quaestor has one or more Deputy Quaestors to assist him or her in these duties.
The quaestor (or deputy, if applicable) supervise the sconce's junior investigative and enforcement personnel, the custodes (sg. custos), and (usually for deputies, if there are any) may directly participate in "fieldwork" for the archmage.
Quaestors existed as a distinct permanent office within an archmagical sconce since the 1000s AE; prior to that, the Archmage either supervised investigations himself/herself or appointed quaestors from among the responsible magi of the sconce on an as-needed basis.