Realms of the Nine Hells

While all layers of the Nine Hells are inhospitable by Faerûn standards, Phlegethos stands out as one of the more memorable. Imagine a land rife with volcanos and lava, chocking black ash, and huge billowing gouts of flame as far as the eye can see. There is not a drop of water to be seen - instead, incredible lakes of liquid fire take their place. This is the realm of Belial, Lord of the Fourth.
One cannot speak of Phlegethos without mentioning the fortress city of Abriymoch, constructed in the husk of a dead volcano of the darkest. Rivers of lava flow from its outer walls, further emphasizing its imposing silhouette over the hellish landscape.
Phlegethos is home to countless lesser fiends, such as the barbed devils and spined devils. Imposing Pit Fiends find employ under the rule of Belial, acting as lieutenants and guards. They in turn command erinyes to serve as messengers and spies. A good number of these devils are under the command of Belial’s many vassals.