Undercity — a maze of catacombs and old sewer tunnels under the capital — is populated with criminals, outcasts, rebels, and the destitute.

The tunnels are cold and damp, smelling of rot and pyre smoke. - Outbreak in Undercity (RPA-ADV3)

An underground network of passages below the capital city of Sabek, where many of the worse-off are left to reside.

While Sabek prospers above, the denizens of Undercity are left poor and unseen;

The locals have a rather low opinion of the King's Guard, and you suspect that they won’t hesitate to infect you if given the chance. - Outbreak in Undercity (RPA-ADV3)