Vile, disgusting things. They crawl around in ruins and tunnels, eating anything that can run away, and then poisoning anything that can -- so they can find and eat it later.
Perhaps considered the "bulette of bugs," the carrion-crawler is a voracious scavenger. They make their nests in ruins and underground tunnels, usually very fond of sewers, and seek out rotting meat of any kind. In most carcasses, carrion-crawlers will deposit a clutch of maggots in order to expand the population.
While it is very easy for sewers and surrounding areas to become swiftly infested by a swarm of crawlers, most cities are quicker in dealing with potential nests by incorporating "sewer patrols." However, cities with power crime syndicates prefer a good population of carrion-crawlers, as it makes disposal of bodies much easier.