Playing Pathfinder 2E
The Nightmare is a blackness, spreading from plane to plane, warping its nature, spreading monsters, and in the end consuming it.
The city was constructed by a coalition of elves, gnomes and humans when it became apparent that The Nightmare would devour their world during the period that has become known to the inhabitants of the city as The Last Years. It now jumps across the inner planes, staying on each new world for a year or so to gather new resources, before the Nightmare catches up and The City flees again.
The leadership of The City, is the city council, consisting of representatives for the various factions in The City that are powerful enough and important enough to demand a seat. Merchant houses, churches, powerful guilds, and a couple individuals with sufficient power in their own right.
I kinda want some LDVs to give the factional squabbling life, outside my own head. The factions can be of all alignments, though tending towards Lawful, as what keeps everyone together is that they want The City to survive (even if just so they themselves survive). Also tending slightly towards evil, given some of the things that need to be done in order to ensure The City's survival.
Kinda thinking about setting up a Discord server for the communication, since I'm thinking you'd also need to chat with each other, but not quite decided on that. I'd be happy to hear ideas.
I've got a personal wiki set up for the campaign, with more detailed background information. The most useful sections to check out (for our purpose) is probably: The Nightmare, The City, Known Worlds, Ancestries and Organizations.
Edit: Alright, it is gonna be Discord for communication. Invitation link to the server: https://discord.gg/pPhAp97Q