Abyss The Abyss ( a - BIS ) was the birth place of the demon s , a chaotic evil universe unto itself with uncountable layers of infinite variety connected haphazardly . The Abyss ' s place in the cosmology of the Forgotten Realms shifted over time , but the nature of the plane remained fairly constant : a violent , malevolent place where the strong survived on the backs of the weak , the weak conspired to overthrow the strong , alliances only lasted while convenient , and the landscape itself tortured the mind and body of all who dared to pass . Cosmology . In the Great Wheel cosmology model , the Abyss was an Outer plane on the Great Wheel connected to the Astral plane , Pandemonium , Tarterus , and Concordant Opposition . It was estimated that the Abyss had 666 possibly infinite layers but no one could be certain . The first layer , named Pazunia after the demon lord Pazuzu , was described as a barren , dusty place baking under a red sun , broken only by great iron fortresses , huge holes in the ground , and the river Styx . Some branches of the Styx flowed down the holes ( which were conduits to the various layers ) and some of these holes supplied water to the Styx in reverse waterfalls . When the Great Wheel model was replaced by the World Tree cosmology model , the river Styx was renamed the River of Blood and it flowed through all the fiendish planes ( except for the Supreme Throne and the Demonweb Pits ) originating in the Abyss , passing through the Blood Rift — an unusual plane that connected the Abyss with the Nine Hells — bringing the demons even closer to their arch - enemies the devil s , resulting in the Blood War . Cosmologists found evidence of portals between the Abyss and the Barrens of Doom and Despair , Clangor , the Demonweb Pits , and Hammergrim , with intermittent portals to Deep Caverns and Fated Depths . The Astral plane connected all of the fiendish planes to the Prime Material Plane , but not directly to each other . After the Spellplague , Asmodeus consumed the essence of the fallen Azuth and ended the Blood War by casting the Abyss to the furthest depths of the Elemental Chaos . The World Axis cosmology described the ruined Abyss as a domain with ever - changing features and realms , where the demons waged futile wars over meaningless empires . Once again the river Styx flowed through the Nine Hells and the Abyss , but then emptied its pollution into the Astral Sea . Other than the Styx or braving the Elemental Chaos , the only known passages to the Abyss were found in the Demonweb Pits , the Dismal Caverns , and Nishrek . Layers . The number of layers in the Abyss was unknown and perhaps unknowable , but this article attempts to list them regardless of which cosmology model was in favor at the time of discovery . Each layer had its own characteristics , which were as varied as the demons themselves . All types of terrain , atmosphere , weather , gravity , and material composition were represented in the myriad layers . Some examples were : Inhabitants . There were myriad types of demons , too numerous to catalog here . Non - demonic life could be found in the Abyss but was most likely imported from other planes . Afterlife . In the Great Wheel cosmology model , chaotic evil souls would travel directly to the Abyss and become mane s , the lowest form of sub - demon . Manes were treated as slaves , cannon fodder , and food by the demon lords . In the later World Tree cosmology model , all souls would first go to the Fugue Plane and await transport to their final resting place . Greedy demon lords would open a portal to the Fugue Plane and conduct raids to steal souls and bring them back to the Abyss to become manes . After the Spellplague , Shar reshaped the Plane of Shadow and folded in what death energy did not get absorbed into the Elemental Chaos and created the Shadowfell . After that , souls on their way to the afterlife started their journey in the Shadowfell and most made it to the Fugue Plane to await judgment , but a few remained behind or were lost . Realms . Relatively few greater powers carved out a realm in the Abyss because dealing with the ubiquitous hordes of demons and ambitious demon lord s would require too much of their attention . Those deities for whom the chaotic evil nature of the Abyss was attractive at some point in time , along with the demon " royalty " whose names were not spoken openly in civil society , were :