The Majority of the information on the Abyss is detailed in the Demonomicon, The Plane Below, and the Manual of the Planes. The Demonic Acolyte template appears in the Dungeon Master's Guide. Information on the war between the Demons of the Abyss and the Devils of the Astral Sea are described in History Check: The Blood War
- The Blood Sea: A roiling ocean of blood that touches all bodies of water in the Abyss.
- The Lair of Anthraxin the Devourer: Floating fleshy isles inhabited by Goriostro Demons and ruled by an ancient and powerful Red Dragon. Detailed in Draconomicon: Chromatic Dragons
- Coagulous: A traveling layer of the abyss, it is home to Codricuhn the Demon Prince known as the Blood Storm. Detailed in Dungeon 172
Layers of the Abyss
The longest official list occurs in the Demonomicon, this shorter list serves as a guide to layers that have been detailed and where to find them.
- 1) Plain of a Thousand Portals: Ruled by Pazuzu and detailed in Demonomicon.
- the Tower of the Ravaastas: Constructed by Larsdana Ap Neut the Arcanaloth sorcerer who is long vanished, now ruled by an Ultrodemon. Described in the Demonomicon and the Dragon article Shemeshka the Marauder.
- Plague-Mort: A human settlement that is possibly a gate-town to the town of the same name in the Shadowfell.
- 4) The Blood Rift: Ruled by Phraxas and detailed in the Demonomicon. The connection to Shemeshka and several Raavasta power brokers who live here are detailed in the Dragon article Shemeshka the Marauder.
- 12) Twelvetrees: Rulerless layer, detailed in Manual of the Planes.
- 23) The Iron Wastes: Ruled by Kostchtchie and detailed in the Demonomicon.
- 32) Sholo-Tovoth: Ruled by Turaglas and detailed in Dragon 376.
- 45-46) Azzagrat: Three layers ruled by Graz'zt and detailed in the Demonomicon. Graz'zt and Azzagrazt are featured in the adventure Court of the Dark Prince.
- 53) Phage Breeding Grounds: Ruled by Urae-Naas and detailed in the Demonomicon
- 65-66) The Demonweb Pits/Court of the Spider Queen: Ruled by Lolth and detailed in the Manual of the Planes, Monsters Manual 3, and Dragon 370 and Denizens of the Demonweb. The Lolth's Chosen theme and Spiderblessed Spinner Template are provided in The Dungeon Master's Guide 2. A skill challenge "Navigating the Demonweb" is given in the Plane Below: Secrets of the Elemental Chaos.
- 69) Gibbering Hollow: Ruled by Ollomegh detailed in Demonomicon
- 88 & 90) Abysm: ruled by Demogorgon Detailed in Demonomicon and Monstrous Manual 2. The Demogorgon Cultist theme and Beast of Demogorgon appears in the Dungeon Master's Guide 2.
- 89) The Shadowsea: ruled by Dagon. Detailed in Demonomicon and Monstrous Manual 2.
- 100) The Barrens: ruled by Oublivae. Detailed in Demonomicon.
- 128) Slugbed: ruled by Lupercio. Detailed in Demonomicon
- 176) Hollow's Heart: Ruled by Fraz-Urb'luu The Demon prince of Deception. detailed in the Demonomicon of Iggwilv Fraz-Urb'luu
- 177) Writhing Realm: Ruled by Ugudenk. Detailed in Demonomicon.
- 222) Shedaklah: Ruled by Jubilex and Zuggtnoy detailed in Demonomicon and Dungeon 188.
- 333) Thanatos: Ruled by Orcus, detailed in the Manual of the Planes and Monstrous Manual. The Orcus' Blood Cultist Theme appears in the Dungeon Master's Guide 2.
- 422) Yeenoghu's Realm: Ruled by Yeenoghu, detailed in Dragon 364.
- 503) Torrenor: ruled by Lamasshtu, detailed in the Demonomicon.
- 548) Garavond: ruled by Haagenti, detailed in the Demonomicon.
- 566) Soulfreeze: ruled by Aseroth, detailed in the Demonomicon.
- 570) Shendilvari: ruled by the Succubus turned Demon Lord Malcanthet described in Ecology of the Succubus.
- 600) The Endless Maze: Ruled by Baphomet, detailed in the Manual of the Planes and in Dragon 369.
- 663) Zionyn: Ruled by Obox-Ob and detailed in the Demonomicon.