Every town in the Vestitas hexcrawl is, in theory, a place you can take over and either own directly or give to a friendly and grateful ally. Several towns are ruled over by secretly (or, as you get further outside the Imperium’s sphere of influence, openly) heretical rulers, so an Inquisition party may find themselves toppling them and selecting replacements as part of their job. A Chaos Cult party might find themselves toppling governments and taking over to drive the Imperium out, to consolidate control over disparate Chaos cults, or just for the lulz.
Rules for what you can do with a town ruled by yourself or a close friend are frequently reprinted in the Rewards section of different hex encounters. This is for reminder purposes only. With the exception of what goods and services are available, all towns have the same rules for rulership.
Gaining control over a one-encounter hex town gives you +1d10 Influence. Gaining control over an urbancrawl town gives you +2d10 Influence. A single character can only command as many towns equal to two less than their Influence bonus (so a character with Influence of 29 or less cannot rule towns at all, even outside Imperium territory where being Highborn is not a prerequisite). Subtract one from the Influence rolled for each town you already control, to a minimum of 1 for a 1d10 hex town or 2 for a 2d10 urbancrawl town. For example, a character who already controls 5 towns would gain 1d10-5 Influence, to a minimum of one, upon acquiring a one-encounter town, or 2d10-5, to a minimum of two, upon acquiring an urbancrawl town.
Having a personal friend or associate gain control over a one-encounter town gives +1d5 Influence, and having a personal friend or associate gain control over an urbancrawl town gives +2d5 Influence. Apply a -1 penalty to the roll for every town whose ruler you’re already associated with, to a minimum of zero. It doesn’t matter how many rulers you’re associated with, just how many towns there are whose rulers you’re associated with, whether that’s being friends with five different mayors or one baron with five towns under his thumb. Party members always count as personal friends and associates, and NPCs that the party has befriended during the story almost always count as personal friends and associates, but backstory NPCs are almost always only friends and associates with the party member they’re attached to, so only that party member gains the 1d5/2d5 Influence for installing them as ruler.
Similarly, a party member may make an Influence check to have a suitable friend on hand to give the town over to, and if two party members have similar backgrounds they may both roll an Influence check, and if they both succeed, they have a mutual friend who can be installed and will both get bonus Influence for it. The GM may allow party members with unrelated backgrounds to roll Influence at a penalty. The GM can also use an influential group of NPCs as a common background element to all PCs, giving them both a reason to know one another in advance and a ready made supply of common associates to hand off any captured towns to.
Characters with Influence of 40 or more do not gain Influence from merely being associated with the rulers of towns (whether one-encounter hex towns or full urbancrawl towns). Characters with Influence of 60 or more no longer gain Influence from ruling one-encounter hex towns. Characters with Influence of 80 or more do not gain Influence from ruling any one town.
While in a town that either they or their associate has control over, a character may use their influence in that town to levy it for goods or services. They gain a +10 to any Influence check they make, and they can also spend 2 Influence to auto-succeed on any Influence check for goods that are locally available (such goods will be listed in the description for individual towns). A character may attempt to roll Influence to special order something from outside of town and have it shipped their, but they can’t levy such an item. Worth noting that in any situation a character may sacrifice 1d5 Influence to auto-succeed on an Influence check, which is worse than paying a flat 2 Influence 60% of the time, as good 20% of the time, and better 20% of the time.
A character who rules over a town directly can also call upon that town’s PDF. This costs no Influence. The PDF answer to the town’s ruler and are obligated to do whatever the ruler tells them to, and they’ll honor that obligation as long as they keep getting paid (mechanically, this means for as long as the ruler’s Influence bonus is high enough to sustain whatever number of towns they rule). A one-encounter town usually has a single PDF squad of ten soldiers, including one sergeant and one corporal, complete with a chimera. An urbancrawl town will usually have one such squad per neighborhood. Some towns may be specified as being more dense with PDF than others.
If the ruler of a town spends or otherwise loses so much Influence that their bonus drops low enough that they can no longer support all the towns they rule, they must either turn that town over to an ally or, if they have no such allies available, allow the town to descend into anarchy completely. Turning the town over to an ally grants Influence to neither of them, and allowing the town to fall into anarchy is likely to result in the town being claimed almost immediately by an outsider. Depending on the town’s location, this is probably either an opportunistic noble from Grey Harbour or an opportunistic warlord from Imberkavitas. The town may also end up being razed entirely by internal strife or hostile forces in the wilderness. Either way, if the former ruler reclaims it from the new owners, they will gain Influence as normal, provided they have since regained the Influence bonus necessary to add another town back into their demesne. Likewise, towns captured do still give Influence bonuses as normal for being recaptured, in addition to any Influence that may be gained for defeating enemies of the Imperium/Chaos/whatever who were occupying it previously.
Intentionally allowing towns to be captured so that they can be subsequently reclaimed is absolutely a scam characters could potentially run, racking up fame and favors amongst the bigwigs back in whichever capital city for pushing an enemy back, letting them reclaim some ground, pushing them back again, on pretty much until the characters get bored or someone else comes to eat their lunch by reconquering the area permanently.