The Shambling Bog

Nearby the sewers, to the other side of the mines, there is a huge underground water reserve. Unfortunately it’s been affected by magic and is an overgrown bog of sorts, with glowing algae.

The place is bright and leads to the sunless sea.

There is a shambling mound or two here, the place has a lot of magnetic jasper and hematite, causing it feel very oddly in terms of auras. Also it distracts compasses nearby. It is not enough to affect metal carried by people, but it someone spends too much time here (short rest) the magnetism causes short term moodiness, granting disadvantage on will saves.

There is a lab of an alchemist down here as well, who studied the phenomenon. They set up lighting rods that reach the surface. And have an electric fence around their lab. The fence is still working, and the shamblers enjoy sticking around it.