|This article is about the current version of DF.|
Note that some content may still need to be updated.
Agents are covert operatives that are sent off to other civilizations' sites to perform tasks, like gathering information.
Mode of action
Agents infiltrate foreign towns and taverns, befriending other historical figures - even hanging out with criminals such as bosses. The friendships are stored asymmetrically - agents consider their 'friends' as information sources, whereas the 'sources' themselves think they made a new friend.
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, monks, 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, and one of your dwarves mindlessly opens their mouth about it, they will sneak back home with the information. Either way, if they come back empty-handed while believing the artifact is at your fortress, they may come to your fortress once again, this time with an army of siegers to persuade you, looming at the edge of your map. 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). Although threatening, ultimatums are always fair: they will never attack you or your messenger while negotiations are ongoing, and even if negotiations go awry, they will let the messenger come back inside first. Moreover, they will never attack you anyway if you give in to their demands.
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.
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 (e.g. a poet with a crossbow*), or their name style and race (e.g. a dwarf with an elven name).
(* This may not be a reliable indicator. Traveling entertainers seem to all[Verify] come with one Level 3 weapon skill, plus supplemental Level 1 combat skills - apparently, the roads are dangerous.)
Another suspect indicator is a migrant with the schemer skill, although more research needs to be done.
Also; visitors with "names" appearing in quotation marks seem to be a reliable indicator that the individual is an agent of someone-or-other, using a false name.
Additionally, if you have any open or cold cases in the justice screen, you can interrogate them to attempt to determine whether they are, in fact, agents seeking to steal your artifacts or perform other nefarious deeds at your fort. If your interogations fail (because your Sheriff or Captain of the Guard has lower social skills than the interrogation subject), but you know the visitor is an agent, you can still convict them (falsely) of crimes and your Sheriff/Captain of the Guard (or other members of your Captain of Guard's militia squad) will attempt to arrest them.
Note that if the suspect is able to evade capture and is about to escape (but is still on your map) you can give them a nickname on their character page (for example, you might nickname them "KILL THIS THIEF"). This nickname will persist after they leave your map and will appear in their name the next time they visit your fortress.
Traitor dwarves were added with the first villainy update. At the time of this edit, next to nothing is known about them except that the concept exists. Clearly, research is needed, although the nature of the subject makes that difficult to replicate or observe.