|Number of layers||Unknown|
|Inhabitants of Abyss|
At places horrid, violent, and disgusting, at others subversive and seductive, at still others deadly at first step to mortals, the Abyss and its many-varied layers cover the breadth of what one might expect from the depravities of the tanar'ri. This plane was once the home of the obyrith thousands of millennia ago, but those beings were largely slain after the War of Law and Chaos by their tanar'ri servitors; since then, the Abyss has been their domain, and they have well held it since that day. The plane under their rule fully embraces the flexibility of chaos, standing on the principle that if there is a horror that can be imagined, it can be found somewhere in the plane. Few safe spots can be found on the plane, and any should be suspected, for here is not a place where any unsuspecting or uninvited mortal ought pass for long.
Given how widely each layer of the Abyss varies, there is no single rule to describe the physical conditions of this plane. Every layer plays by its own rules in form and danger, each with its own binding theme, or its own Abyssal lord deciding what horrors are to be found here. However, there is a general rule any traveler to the Abyss should be aware of if they haven't been put in the dead-book right off the bat. When exploring this plane, always keep three priorities at the forefront of your mind: survive the layer's terrain and climate, avoid being eaten, and find enough untainted rations to keep from starving.
Beyond this, all a basher should know is that if they can imagine a form of inhospitality, it exists somewhere on the Abyss. From areas so filled with beings that the mere pressure can crush you alive to endless oceans of acid to forests of trees that attempt to eat you alive to layers that gnaw at your very personality and twist you to evil, there's no end to the variety and, admittedly, creativity to what the Abyss can conjure up to terrify and torture mortal and immortal alike. Out of all the Lower Planes, many would say that the Abyss is the best contender for the most common Prime conception of Hell.
|Conjuration||Any calling or summoning spell has a chance of calling a curious tanar'ri rather than the intended result equal to 10% per level of the spell.|
|Divination||True tanar'ri and Abyssal lords are always aware of any divination spell cast against them when on their home plane, and can use the spell to strike back at the caster; clairaudience might be used to issue a sonic attack, for example, or clairvoyance could grant a visual counter. Detect magic is the sole exception, allowing any sort of counterattack. There is a limit to how much can be sent back along the path of the spell, however. Only up to twice the level of the divination spell in total spell levels can be sent to the mage.|
|Illusion||Illusion spells cast in the Abyss are heightened by 1 spell level.|
|Necromancy||Animate dead works, but the undead created by this spell on the Abyss can be possessed by petitioners, manes, or other lesser creatures, which often results in the undead turning on the caster. Reincarnation on the Abyss always results in the individual returning as a tanar'ri; usually a dretch or manes, but rarely a rutterkin or lesser tanar'ri. Good-aligned people return as bodaks.|
|Transmutation||Whenever a transmutation spell is attempted, the recipient must make a Fortitude save at DC 15. If this save succeeds, the spell works as normal; if it fails, the transmutation is distorted in some manner as detailed below.|
|Elemental||Protective spells usually fail when they are needed most; upon any attack or exposure to harmful environment an elemental protective spell is meant to defend against, the caster or recipient must make a Will save at DC 15 to determine if the spell or item functions properly. Destructive elemental spells are enhanced, causing an additional point of damage per die.|
The most dangerous aspect of arcane magic on the Abyss is attraction from the demons that fill it. Tanar'ri have no great love for mages, given how often they attempt to summon and bind their kind to the Prime. Thus, any signs of a powerful one on the Abyss are likely to bring quick and decisive retribution. True tanar'ri and Abyssal lords can sense any usage of magic on their layer, and often twist the magical paths to strike back upon their casters; while spells that effect only the caster and her friends are likely to avoid retaliation, spells that directly affect a tanar'ri without causing actual harm may bring a headache, ones which cause harm to lesser tanar'ri might bring a sudden bout of leprosy or a plague of manes, and spells striking against greater or true tanar'ri will almost certainly bring a direct response from the plane's lord. Certain spells are also more likely to bring retribution than others; spells of binding or coercing demons are the most likely, followed by offensive spells, defensive or warding spells, and finally spells that trick or inform are the least likely.
Transmutation spells are especially affected by the chaotic nature of the Abyss. The most minor of changes, those that cause minor changes in properties but none in form, cause only slight corruptions; flame arrow conjuring several fiery bats, for example, or a flying character sprouting wings from the neck or ankles. Those that cause massive changes in properties without altering form are more distorted, creating unintended though temporary side effects. Pyrotechnics might create a splash of lava, while control weather might bring about a sudden storm of acid rain around the caster. The worst corruptions come from those that alter physical form. Living recipients may change species towards a more corrupted nature - humans becoming tieflings, for example, or elves becoming drow - while nonliving recipients become foul and useless. Side effects are often more lethal as well, and may affect more than just the caster. Statue might petrify the caster, while gaseous form might become permanent. See list of Abyssal spell alterations for a full list of which spells fall under which category.
Spell keys in the Abyss most often involve blood or money, in the form of bribes to a layer's lord. Necromancy spells might require a death, elemental spells a fouling of some pure material, and transmutations a mingling of the caster's and recipient's blood. The keys for a given type of spell often change by layer or simply over time, however, as befits the chaotic nature of the Abyss. The keys for Divination spells are the most well-kept secret of them all, as no tanar'ri likes the idea of being spied upon.
See Lexicon of the Abyss.
- Bugbear Pantheon
- Dwarven Pantheon
- Drow Pantheon
- Faerunian Pantheon
- Giant Pantheon
- Kostchtchie - Strength, violence
- Gnomish Pantheon
- Urdlen - Greed, bloodlust
- Krynnish Pantheon
- Vedic Pantheon
- Kali - Life, death
- Baphomet - Minotaurs, battle, beasts, uncontrolled nature
- Demogorgon - Ixitxachitl, energy drain, domination
- Eshebala - Foxwomen, vanity, charm, cunning, greed
- Gorellik - Gnolls, hunting, hyenas
- Great Mother - Beholders, magic, fertility, tyranny
- Juiblex - Unknown
- Kanchelsis - Vampires, blood, magic
- Laogzed - Troglodytes, eating
- Merrshaulk - Yuan-ti, poison, somnolence
- Ramenos - Bullywugs, somnolence, decay
- Sess'innek - Lizard kings, dominion
- Vaprak - Ogres, combat, greed
- Yeenoghu - Ghouls, gnolls, paralysis
- On Hallowed Ground, pp.172-182
- Planes of Chaos - Book of Chaos, pp.12-33
- Planewalker's Handbook, pp.14-15