The Pits

Legend of a legend, the Pits are crevices, land chasms and abandoned mines scattered in many deserted places, none of which has been exactly defined, but that mostly seem to lay at the feet of the mountains, particularly of those parting the Empire from the Four Realms, and the southern Grey Boulders. The Pits are thought of as gateways to the Underworld, where underlings originally came from and even more powerful, evil subterranean races dwell along with monsters too horrid for the light of the Sun. Dwarves are the most convinced believers in the existence of the Pits, and claim several have been discovered during their diggings, costed them many a young warrior, and been covered again with the sturdiest Dwarvish stone walls. Pits are thought to stand unidentified as such for many years, until beings from below notice them, and come out in moonless nights to prey upon the unsuspecting surface-dwellers.
The picture on the left represents the popular view of a Pit, a hellish gigantic maw spitting motley and oddly deformed underlings. Needless to say, if actual pits exist, they probably look more sober than that.