They didn’t ask permission to move in. They just moved.
A regional thieving power that took Citavas Port City's underworld by force, and started a war doing it.
The Roof Runners are a thieving guild with reach well beyond Citavas Port City, prominent enough across the region that when their Guildmaster decided to set up shop in the city, the smaller, already-established local guild simply got absorbed rather than competed with. The takeover was clean by guild standards. It was also the spark for a guild war that has cost Citavas Port City numerous lives since.
Like every guild operating in Voir, the Roof Runners answer to an unwritten arrangement with the Monitors. Heavy tithes to the church buy them a strict blacklist of untouchable marks: Iüdex clergy, major donors, church-protected merchants. Anyone not on that list is fair game, provided the guild keeps its business out of Monitor's specially protected. It's this arrangement that keeps the Monitors from simply wiping the guild out.
The guild's real highway isn't the street. It's the Aetherstride, or just the 'stride,' Citavas Port City's rooftops, dense and multi-story enough that a Roof Runner can cross half the city without a boot ever touching cobblestone. It's fast, it's largely invisible to the Monitors patrolling below, and lately it's gotten contested: pockets of the stride the guild used to move through freely now belong to someone else.
What almost nobody in the guild knew for years is that the war itself didn't start the way anyone thought. An autochthon infiltrator passing as an elf, Deor'c Aelf, spent years inside the guild's own ranks feeding it a slow diet of lies about the Night Runners, all while doing the exact same thing on the other side. The truth's out now. It didn't make the war any easier to stop.
Guild slang for a Roof Runner who came up through another calling first, their own version of "Mustang."