For instance, the players might find their path to the A Gate blocked by a barricade that requires them to travel back through the Merchant Quarter to reach the Engineering District and secure an explosive. However, the plans for that explosive require reagents that send them searching both the Merchant Quarter and the Arcanum. By the time all that’s done, they’ll have the explosive necessary to take down the barricade—but the various factions will have shifted and battled in the meantime. The barricade may have already been removed through the main strength of bugbears, or overrun by feral squirrelmen. Squirrelmen are absolutely a real thing in this campaign.
Since Zak S mentioned the 25-word campaign descriptions idea, I’m going to use that to briefly sketch out the nature of each zone and what the players can expect there…perhaps not in 25 words, but I’ll at least shoot for that many. That makes this a work in progress.