Carceri

Tarterus was a plane that the Companions of the Hall reached by means of the Taros Hoop of Pasha Pook.

Description
The only visible features of Tarterus were clouds of black smoke that whirled about, revealing hundreds of twisting stone bridges arching underneath. None of these bridges were more than a few feet wide. There was no evidence of land underneath the bridges, but only bridges over bridges and smokey void beneath.

The plane of Tarterus featured heavier gravity than Toril's, distorted gravity, and strange physics, making it seem directionless. Bruenor Battlehammer's dwarven direction senses indicated they were climbing upwards, even though his eyes told him that a bridge they had recently left was now higher than he was. When Cattie-brie fell from one of the bridges, she reappeared in the sky above them, looping through the circular plane.

Inhabitants
Tarterus was inhabited by demodands.