Legati may negotiate with barbarians. The diplomacy screen can be found at the Graecostacium (a building at the Comitium).
Conquest of a region or location on the map, opens that region up. Mines, quarries, clay pits and free farmland may be available in a region that is conquered by Rome.
Keep in mind that regions may also be lost to barbarians, if they reconquer or conquer an area previously held by Rome. Therefore in times of war it is prudent to defend such areas with a Roman legion, especially areas deemed strategically or economically important.
Tribute
In some instances barbarian factions may give tribute to the Roman state and vice versa.
Foreign Trade
Barbarian traders may visit a market fair in some situations. They will sell certain resources. More information about barbarian trade can be found here.
Foreign Factions
More information about barbarian factions can be found here.
Foreign Attitude
The following list shows the possible stances that a barbarian faction may have:
Hostile acts tend to negatively influence the stance of a barbarian faction, while friendly acts tend to positively influence the stance of a barbarian faction.
Foreign Culture
The following list shows all the various cultures of barbarian factions that may exist in the game:
The culture of a barbarian faction is one major aspect that influences the behaviour and appearance of barbarian forces on the worldmap and battle map.