Cobalt Labyrinth

A winding natural maze of santstone and marble inlaid with cobalt veins, the cobalt labyrinth has been a place many a wealthy ruler has wished to acquire. But there’s hardly anything profitable in your miners going in and never returning with the valued cobalt…the ones that do return never really quite seem the same.
There is not a single person in living or dead history that understands what makes the labyrinth as dangerous and mind bending as it is. Mages detect no magic, and survivors tell no tales. It is as if their very souls have been left behind within those stony walls never to be seen again. And their minds reveal nothing. Simply empty. But there is never heard a living voice when no one has adventured in. Nothing dead seen. Nothing at all.
There have been a very few heroes of grand strength that have gone in before. Most did not return, and the few that did were much the same as the common man that had entered. Those few that retained any part of their mind could not remember, or simply would not let themselves remember what they had seen. Forever hollow with eyes turned a cobalt hue...