A key gameplay element in Age of Wonders 4 is the free cities that dot every map. Much like city-states in Civilization 6, free cities use similar mechanics as regular factions but have no interest in expanding beyond their capital.
The other big difference between factions and free cities in Age of Wonders 4 is the way diplomacy works when interacting with them. Instead of balancing out relationships and treaties, players can quickly get free cities onto their side with a few simple interactions. Over time, these cities will swear fealty, but players can end up competing with other factions to be the first to turn a free city into a vassal.
Free Cities and Whispering Stones
Every faction in the game starts with at least one Whispering Stone. Diplomatic factions can start with multiple Whispering Stones, and there are ways to get more from the Imperium tech tree.
Once a faction discovers a free city, they can select it to bring up a simplified diplomacy screen. Assuming the free city doesn't declare war on the faction for whatever reason, players can give the free city a Whispering Stone that slowly increases the city's Allegiance stat. The faction starts with a neutral relationship, and as Allegiance grows the free city will swear pacts of cooperation, loyalty, and then vassalage.
Each level of pact opens up new interactions with the free city. The Pact of Cooperation opens up trade options, which players can select from the free city's diplomacy screen. This includes magical materials, and every free city has at least one magical material. The Pact of Loyalty allows factions to build on claimed provinces without complaint, and they start contributing to the Rally of the Lieges. The Pact of Vassalage has the city start contributing its income with their overlord, and they'll go to war with their overlord's enemies.
However, a free city can only have one overlord, and even AI factions are aware of how valuable a vassal free city can be. That's why players will often find themselves competing with other rulers to be the first to secure a free city's fealty, because once they swear a Pact of Vassalage to one faction they become off-limits to everyone else. If another faction gets a free city as a vassal, the only way for players to get it is to declare war against their new overlord.
Fortunately, players can see exactly how close every faction is to reaching the Pact of Vassalage on the free city's diplomacy screen. The green Allegiance bar has a shield for every faction trying to improve their relationship with the free city selected, and the shield that's farthest to the right indicates the faction that's closest to securing a Pact of Vassalage. If players are behind, they can spend Imperium to jump ahead. However, players can only spend Imperium once during each pact level, and the other factions can spend Imperium to do the same thing.
Players can also improve Allegiance gain in other ways. Magical materials, spells from certain tomes, and Imperium upgrades can all improve the amount of Allegiance a Whispering Stone adds each turn.
Vassalage Levels and Integration
Once a free city has declared fealty to an overlord, or once a faction conquers a free city and releases them as a vassal, their relationship enters a new stage. Players should keep their Whispering Stone with their new vassal because the benefits of this relationship continue to improve as Allegiance increases.
A free city that declares the Pact of Vassalage will enter this new relationship as a Vassal, which means they share 30 percent of their Gold, Mana, and Knowledge incomes, they give their overlord free access to their magic materials, and they contribute 2 points and special units to the Rally of the Lieges. On top of that, players can hire new heroes of the vassal's race, and their territory counts as friendly for healing units.
As the city's Allegiance grows, they'll become a Bonded Vassal, Flourishing Vassal, and finally, a Supreme Vassal. Their contributions grow to 50 percent of their income and 5 points for Rally the Lieges, and starting at Flourishing Vassal, players can integrate a free city into their faction.
Integrating a vassal has a large Imperium cost based on the city's population size, and an integrated city counts against the faction's city cap while there's no cap on vassals. On the other hand, the city's leader will join the faction as a free hero with a decent set of magic equipment, and players can choose the race of the integrated city when building new cities.
A conquered vassal will usually start out as a tributary instead of a full vassal. This means they'll share less of their income and demand more from trades instead of less. Players can also vassalize other factions by defeating them, at which point the faction loses the game and starts behaving like a vassalized free city. However, players will still be able to use the full set of diplomacy interactions with the conquered faction and can break the vassalage if they like, and they can never integrate a faction vassal.
Age of Wonders 4 is available now on PC, PS5, and Xbox Series X/S.