Undercover Network, also known as the Spy system, is a gameplay mechanic introduced in Total War: Three Kingdoms. Similar to the Agent system from previous titles, player can engage in subterfuge and clandestine means such as spies and espionage to gain information, influence and advantages in campaign and in battle.
There are no dedicated Spies or Diplomat in Three Kingdoms, all characters can perform all roles (unless they don't want to do undercover work).
Completely neglecting spies is reducing the player's toolset, which means player'll have to rely more on traditional methods - Like diplomacy or violence.
If player are too paranoid, placing a closely knit set of people in the important positions, like faction leader's family, will probably help because the player can trust family relation by a degree. So, Sun Jian is an excellent faction to play a bit more spy-free game because of his strong and close family connection.
Some characters in player's faction will be willing to spy on other factions, and perform acts of espionage to weaken those competitors in a variety of ways.
If a character is suited to spying, player will see an eye symbol next to their title rank in characters list or character information panel. Player also need to have an available spy position, the first of which unlocks at the faction rank of second marquis. Further spy slots can be unlocked as the faction rank advances or by researching new reforms.
With an available spy position and a character willing to spy, player can click the undercover network icon at the top of the main campaign screen to dispatch a spy, or manage existing spies’ activities.
Dispatching a spy involves releasing them from player's service (at least for appearances' sake!) and choosing a faction for them to infiltrate. This sends the spy to seek employment with the target faction, and causes the spy to appear in that faction’s list of candidates for recruitment. More attractive candidates – ie, those of higher level and experience – are more likely to be recruited into the target faction. This may take a number of turns – or may not happen at all, if the targeted faction doesn’t find player's spy desirable. Player can check back on their progress from turn to turn by opening the undercover network panel again and selecting the dispatched spy.
If a dispatched spy is recruited by the target faction, player will gain visibility over many of their details, such as their employed characters, their commanderies and their armies. A number of new spy actions will also become available. These rely on the spy building up two specific resources: cover points and undercover network.
Undercover network points
Once a spy is dispatched, they will begin building a network of contacts, informants and other covert assets, represented by player faction's undercover network value. This is contributed to, and shared between, all of the dispatched spies. Spy actions cost undercover network points to perform as noted on each action; the more advanced the action, the higher the cost.
As time passes for an active spy who has infiltrated another faction, they will will seek to establish trust with those around them, and will begin to build personal cover points. The higher their cover points, the more likely the spy is to successfully perform spy actions without being revealed. Each action costs some cover points to execute, as noted on the action.
There is always the risk of a spy being caught in the act and revealed when performing a spy action. The more cover points a spy has, the more this risk is reduced.
If a spy becomes revealed due to an action, the warlord of the target faction will have a choice of executing them, releasing them back to their original faction, or demanding they return to their original faction as a double agent. In this event, the warlord of the original faction will only know that the spy has been returned unharmed to their original service. A spy who has been revealed will never be able to spy again for his original faction.
Factions can make it harder for spies to operate against them by increasing the cover points cost and/or undercover network points cost for any enemy spy actions that target them.
The Drum and Bell Tower building, characters with counterintelligence traits inhabiting the ministerial roles of faction leader, prime minister and faction heir, certain ancillaries, certain reforms, and certain strategist assignments can all increase the points costs for enemy spy actions.
List of Spy Actions
Spy actions fall into four categories, based on the position a spy is appointed to in the target faction. Each action carries its own cover point and undercover network point cost, and performing the action generates a dilemma which may increase the risk of the spy becoming revealed.
Court noble actions will be immediately available to a spy if he is recruited by the target faction. These actions include boosting the existing undercover network, influencing trade, theft, reducing character satisfaction, seeking a career as a military general, and interfering with the faction's counter-espionage efforts.
Administrator actions become available when a spy is appointed as administrator of a commandery owned by the target faction. These enable the spy to weaken aspects of the settlement and its garrison, pursue a ministerial role in the target faction's court, incite low public order or rebellions, or publicly defect, granting ownership of the spy's administered commandery to the player.
General actions become available when the spy is appointed as a general in one of the target faction's armies. These actions offer a range of sabotage options against other armies in the target faction, and inciting a military revolt, which grants ownership of the spy's army to the player and causes the army's other generals to be recalled to the target faction.
Family subterfuge actions become available when the spy is adopted as heir or marries into the family of the target faction's leader. These enable the spy to improve the target faction's diplomatic attitude towards player faction, assassinate the target faction's heir, and even its faction leader.