Agent

Agents are covert operatives that are sent off to other civilizations' sites to perform tasks like gathering information.

Agents usually arrive at your fortress as visitors, assuming the identity of an artist, warrior or scholar. In addition, outside your fortress, they may also pose as pilgrims, peddlers, prophets or petty criminals in other sites.

Agents typically want to know about the whereabouts of an artifact. In fortress mode, they will arrive at your tavern and chat with your locals and other visitors to gather information. If the artifact is not at your fortress, they will use the rumor system used by other visitors and your diplomat to find out where to go next. If you do have it, they may demand that you give it to them, or simply sneak back home. Either way, if they come back empty-handed while believing the artifact is at your fortress, they may come back with an army of siegers to persuade you. At this point you may either give in (resulting in the army retreating peacefully with the artifact) or fight back (resulting in a regular full-blown siege).

You may draw the ire of a civilization and its agents by stealing artifacts from outside (as opposed to making your own) in a mission.

Due to a bug, agents from your own civilization may retain their assumed identities when immigrating to your fortress.^Bug:10490 These agents remain loyal to your civilization (at least for now).

Detection

Agents use false identities and cannot be forced to reveal their cover, but they can be manually detected by the player by looking at discrepancies between their self-styled profession and actual equipment or skills, or their name style and race (e.g. a dwarf with an elven name).