From publisher blurb:
Welcome to “100 Oddities for a Sewer,” the eleventh entry in Skirmisher Publishing’s bestselling “100 Oddities” series of universal mini-sourcebooks! Sewers figure in a lot of roleplaying games, especially those set in or involving cities and, from the lowly rat-slaying forays of fledgling heroes to quests against monstrous beasts that dwell within them, they can keep adventurers busy. They also can allow travel below, to, or through intervening places (including those you might want to visit even less than the sewer itself). They might also be a haven for criminal elements or street folk, or a hideout for those who cannot stand scrutiny by the light of day.
Sewers exist from age to age, and could figure in an ancient setting as easily as a modern or future one (heck, the same sewer might be found in all three). And, as far as post-apocalyptic setting goes, the sewer is often where all the best mutants hang out.
If there is any place that will have its fair share of oddities, therefore, it is a sewer, and we have provided 100 great ones for you here.