Capcaps
Almost everyone has heard about the tunnels and passageways that riddle the earth below the city of Salt in Wounds the so called Cap-caps. Unfortunately much of what is known is incorrect, the product of speculation, hear-say, and unsubstantiated rumor liable to get a would-be explorer hopelessly lost. The Capcaps are an odd mix of ever-changing ankheg hunting-tunnels, the ruined vaults and halls of the sepulchral duergar city of CarDouf as well as the mishmash of (more recent) excavations by sentient creatures that connect and build off the other two. These range from meter wide tubes which can only be crawled through to cavernous amphitheaters which seat hundreds. None of these are sewers although some waste and refuse of various kinds do seep into them as instead most sewage is generally dumped into the Red River. God-Butchers dig testing wells straight down in order to make seasonal forays into these tunnels with the specific aim of securing and destroying any underground access to Salzinwuun in order to slay or drive out the ankhegs that dig their way to the prone Tarrasque to feed. Otherwise the Capcaps are left unpatrolled and as such are favored haunts of smugglers, monsters, and other secret forces drawn to the city but unable to operate in the open.