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Cities 101
Capital Cities, Port Cities, City Zones, Building, Regent, Claiming a City, Cities of Erfworld

[edit] Proposed Canon

Warlords may claim a city that is not currently controlled by any Side.^Erf-b1-p078 This act places the city under the command of the Warlord's Ruler.

Barbarian Warlords can create a new side by claiming^Erf-b1-p078 or rebuilding^Erf-b1-p099 a city on a Capital Site.

It is also implied that any warlord could, theoretically, claim a city. Due to having Loyalty to the side that Popped them, this could be a way for a side to create a number of puppet sides

[edit] Speculation

It is possible that all Commanders, including Casters, may claim a city, or that this can only be performed by Chief Warlords.