From publisher blurb:
Nowhere in Castorhage are the simple laws of the natural food chain more apparent and clear than in the lowest levels of the Underneath. The denizens of the dark and mysterious passages below the city streets are the hunters and the hunted, chasing prey through the uncharted tunnels of the Nether while running from more deadly predators than themselves. Although solitary dwellers may succeed in quietly luring prey and escaping their enemies for a while, large bands of creatures have better chances of long-term survival. Small villages and large towns in the darkness belowthe surface aren’t by any means safe places, but at least residents can see their assailant coming; in the dark depths of the Underneath, the death screams of the lone wanderer are often never heard.
Not every creature of the Nether chooses a solitary existence. Althoughsome creatures leave their settlement to avoid paying a debt or to flee anassassin, most return when the dust settles. It is safer to take their chances with what they can see and hear than to try to survive in the tunnels all alone. However, not every creature can return to its village or town. The most egregious offenders of settlement laws are punished with a fate worse than death: exile. They are banished from their homes and pushed into the lawless and unforgiving realm beyond the safe walls to which they’ve become accustomed. They will be alone, easy prey for hungry tunnel people who wait in the shadows at the outer edges of well-traveled passages and caverns.
The Exiled (as they are called by the Underneath dwellers who encounter them) are burned with a magical insignia on their face or head that lists the settlement, the date and their crime. Any who meet one of the Exiled immediately knows the details of their banishment, and can easily refuse their entry into their village or town. The skin etching glows a faint red and can be seen through clothing, paint, or hair. Not every village and town in the Underneath uses this method to identify the Exiled, but for the sake of this adventure, most of the humanoid monster settlements have turned to using the burning stamp to keep undesirables out of their villages.