From publisher blurb:
Appendix N literature is filled with cities, glorious or decaying. Beneath the streets of these urban centers lies a region dank, foul with the effluvia of countless generations, flowing through crumbling brickwork in the malodorous darkness. If your players are anything like mine, sooner or later they will wish to have their characters delve into these fetid morasses.
This product is intended to ensure that you are ready. To that end, a small area of sewers is described, with several hooks to entice PCs into investigating. Three appendixes supply added content to expand the original area or to create sewers of your own. The last appendix is an abbreviated patron write-up of Squallas, Mistress of the Night Soil Rivers, whose domain is the sewers.
Campaign Elements 9 - Both Foul and Deep written by Daniel J. Bishop, is a campaign element to designed for 4-6 level 1-2 PCs, with the tools to help you create a rich campaign environment for PCs of any level.