From the introduction:
The village of Carlsburg stands as an end to the Dragon Empire’s longest trade road, ripe with grapes and wine. Most make their way in life by farming, ranching, making wine in the cellars, or working the inns and taverns. The denizens of Carlsburg are an easygoing sort — so long as the soil is fertile. And the soil is always fertile.
Deep underground, beneath the sewers, another service is offered. A vast catacomb accepts the departed (dearly or not) from as far away as the capital. This would normally poison the land above, destroying crop yields and worse still—souring the wine. However thanks to a fungus affectionately called, Gloom, the poison of rot is consumed and in its wake is left an incredibly nutrient rich compost.
Lately though, new tunnels have been appearing on their own. Old corridors seem to move or disappear completely! What the devils is going on down there?