An aboleth has a pink belly. Four pulsating, blue-black orifices line the bottom of its body and secrete gray slime that smells like rancid grease. It uses its tail for propulsion in the water and drags itself along with its tentacles on land. An aboleth weighs about 6,500 pounds.

Aboleths are cruel and highly intelligent, making them dangerous predators. They know many ancient and terrible secrets, for they inherit their parents' knowledge at birth and assimilate the memories of all they consume.

Aboleths are smart enough to refrain from immediately attacking land dwellers who draw near. Instead they hang back, hoping their prey will enter the water, which they often make appear cool, clear, and refreshing with their powers of illusion. Aboleths also use their psionic abilities to enslave individuals for use against their own companions.

Most races maintain as part of their culture elaborate creation myths, stories they pass down through the generations with great respect, for these myths tell of how their race came to be. Often, one race's creation myths are at odds with another's, but this is of little concern, since a conflicting tale can easily be discounted as sheer fabrication. The aboleths, however, do not have such myths, for a simple reason. They believe it an indisputable fact that they were the first, the primal race that existed before nearly all else, second only to the unknowable Elder Evils that spawned them. They know this because they remember the ancient past with crystal clarity. All else in the world is a pale imitation of their primal perfection. Even the deities themselves are subject to derision, for the aboleths know that they predate the gods. They have seen the world destroyed countless times by apocalypses both natural and artificial, yet each time the world remade itself and the aboleth survived. They are truly nightmares out of time.

Sages speculate that cildabrins might be a created race, not one that evolved naturally. Those who espouse this theory point to the aberration's remarkable similarities to two other natural kinds of arachnid creatures: hunting spiders (such as tarantulas) and scorpions. Cildabrins seem incapable of true speech but can communicate with other arachnids. They are sentient; they merely lack the means to vocalize sounds.

When roaming underground, cildabrins sometimes stray perilously close to dungeons, sewers, crypts, and other subterranean elements of civilisation. Despite legends to the contrary, it does not seem that that cildabrins are tools of the drow. The dark elves fear these terrible beasts as least as much as other humanoids do. In fact, some religious sects among the drow consider the appearance of a cildabrin to be a dire omen. For their own part, these aberrations seem to prefer dwarf flesh above all else.

A gibbering mouther is a creature seemingly drawn from a lunatic's nightmares. Although not evil, its thirsts after bodily fluids and seems to prefer the blood of intelligent creatures. Sometimes the arrangement of eyes and mouths on a gibbering mouther's body resembles a face, but just as often the features have no relationship to one another.

A gibbering mouther is about 3 feet across and 3 to 4 feet high. It weighs about 200 pounds. Gibbering mouther's can speak Common, but seldom say anything other than gibberish.

Truly hideous in appearance, brain collectors have bloated, yellow-orange, oily bodies that spout dozens of short, writhing tentacles. Ten slightly longer tentacles frame its lamprey mouth, which is filled with row after row of jagged teeth. Above the gaping maw are four large, yellow, red-irised, bulging eyes, behind which cluster a number of squirming bulges about a foot across.

These bulges house the human or humanoid brains the brain collector has harvested to date (up to thirteen brains at a time), which it uses to power its own special abilities. It must discard one of its currently 'banked' brains in order eto replace it with another. The creatures move with surprising agility on segmented, crablike legs. Brain collectors lack fixed internal anatomies and can rearrange organ functions at will, making them very difficult to kill.

Brain collectors hail from a distant reality known to sages only as the Far Realm or the Nightmare Dimension. Occasionally juveniles are encountered in isolated locations, but fully grown specimens are quite rare. Both types visit mundane realms in order to harvest the brains they need to fully access their abilities. A juvenile will seize brains as the opportunity arises, but an adult absorbs only the brains of arcane spellcasters, passing along rejects to less fussy mind flayer retainers. A creature whose brain has been harvested by a brain collector cannot be raised, reincarnated, or resurrected while the brain is in the creature, because the collector preserves and draws upon the soul and basic personality of the creature for as long as it retains the brain. A brain collector might be bargained with for the return of a specific brain, but only in exchange for a better (more powerful) specimen.

Brain collectors typically attract a retinue of mind flayers, drawn by the desire to study the aberration's technique in extracting brains with ranged attacks and its ability to access the arcane brainpower of the assimilated brains. Some sages have ascribed the illithid's attraction to simple self-interest (the illithids get to claim the rejects that do not meet the neh-thalggu's demanding specifications), others to an affinity almost amounting to worship. On rare occasions a neh-thalggu is accompanied by a single paragon mind flayer sworn to its service.

Neh-thalggus' own language is a silent sign language 'spoken' with their tentacles. They can also communicate telepathically with any creature that has a language within 100 feet.

An eidolon is built of ancient rock, basalt, porphyry, obsidian, or other igneous stone. Its surface is covered with ancient runes or glyphs from forgotten, dead languages. While the features of an eidolon might appear somewhat eroded or timeworn, the creatures remain quite sturdy and dangerous. Eidolons are mindless, and do only what they are ordered to do by their creators. The process for creating eidolons has long since passed into antiquity, so eidolons that still exist are generally without masters. They continue to perform their prior tasks, relentless and eternal in their obedience. These instructions must be simple, such as "Remain here and attack any humanoids that enter this room" or "Patrol the perimeter of this building." Often, the focus of an eidolons task has long since crumbled away, yet the construct continues to guard or patrol for aeons after the location itself has gone to dust.

Damaged eidolons repair themselves quickly, or can be repaired in an appropriate workshop or laboratory.

An eidolon is built of ancient rock, basalt, porphyry, obsidian, or other igneous stone. Its surface is covered with ancient runes or glyphs from forgotten, dead languages. While the features of an eidolon might appear somewhat eroded or timeworn, the creatures remain quite sturdy and dangerous. Eidolons are mindless, and do only what they are ordered to do by their creators. The process for creating eidolons has long since passed into antiquity, so eidolons that still exist are generally without masters. They continue to perform their prior tasks, relentless and eternal in their obedience. These instructions must be simple, such as "Remain here and attack any humanoids that enter this room" or "Patrol the perimeter of this building." Often, the focus of an eidolons task has long since crumbled away, yet the construct continues to guard or patrol for aeons after the location itself has gone to dust.

Damaged eidolons repair themselves quickly, or can be repaired in an appropriate workshop or laboratory.

A shaboath is about 10 feet wide, with 10-foot-long tentacles. It weighs about 12,000 pounds.

A shaboath cannot speak nor make any vocal noise. The creature carries with it a distinctive musty smell, like that of mildew or swamp water. On land, it moves with a sloshing, undulant coiling, and leaves a trail of moisture in its wake.

Marids look like tall, blue-skinned humans. When they deign to wear clothing at all, it's something that won't impede swimming. Some marids dress in finery woven entirely from seaweed, with a brocade of coral and pearls.

As a group, marids have a much looser social structure than other genies. On the Elemental Plane of Water, there is a loose empire ruled by a padishah, but many marids don't recognise its authority. At any one time, there are a number of heirs vying for the Coral Throne - and many are unwilling to wait for the current padishah's reign to end naturally.

Witchlights, like wisps, can speak common, by producing vibrations in the air, resulting in a ghostly sounding voice, which they often use to lure unwitting souls to grisly, painful, and protracted deaths.

Although most people shun contact with these loathsome creatures, sometimes avoiding them is simply not possible. Kuo-toa know much about long forgotten, ancient evils dwelling in the deepest parts of the ocean.

An average kuo-toa stands roughly 5 feet tall and has a more or less humanoid appearance. Its rounded body is covered with fine scales giving it the appearance of being pudgy or bloated. The arms and legs are slender, almost willowy, ending in broad hands and distended feet that look very much like flippers. The bullet-shaped heads are piscine, with bulging, silver-black eyes and wide mouths full of needle-sharp teeth. Although kuo-toas are generally a silver-gray colour, their pigmentation changes with their mood. An angry kuo-toa is dark red, while a frightened one becomes pale gray or even white. The air around a kuo-toa carries the almost overwhelming odour of rotting fish.

Kuo-toa are an obvious choice as allies for the aboleths for many reasons. First, they are individually much weaker than the aboleths and can be bullied into servitude. Second, they are amphibious and can carry out their masters' plans on the surface. The aboleths keep the kuo-toa docile with their enslavement powers, but favoured kuo-toa leaders are allowed to keep their own minds as a reward for good service. Since most of the other kuo-toas remain enslaved, the aboleths have no fear that the few free-willed kuo-toas can engender rebellion.

Although most people shun contact with these loathsome creatures, sometimes avoiding them is simply not possible. Kuo-toa know much about long forgotten, ancient evils dwelling in the deepest parts of the ocean.

An average kuo-toa stands roughly 5 feet tall and has a more or less humanoid appearance. Its rounded body is covered with fine scales giving it the appearance of being pudgy or bloated. The arms and legs are slender, almost willowy, ending in broad hands and distended feet that look very much like flippers. The bullet-shaped heads are piscine, with bulging, silver-black eyes and wide mouths full of needle-sharp teeth. Although kuo-toas are generally a silver-gray colour, their pigmentation changes with their mood. An angry kuo-toa is dark red, while a frightened one becomes pale gray or even white. The air around a kuo-toa carries the almost overwhelming odour of rotting fish.

Kuo-toa are an obvious choice as allies for the aboleths for many reasons. First, they are individually much weaker than the aboleths and can be bullied into servitude. Second, they are amphibious and can carry out their masters' plans on the surface. The aboleths keep the kuo-toa docile with their enslavement powers, but favoured kuo-toa leaders are allowed to keep their own minds as a reward for good service. Since most of the other kuo-toas remain enslaved, the aboleths have no fear that the few free-willed kuo-toas can engender rebellion.

Although most people shun contact with these loathsome creatures, sometimes avoiding them is simply not possible. Kuo-toa know much about long forgotten, ancient evils dwelling in the deepest parts of the ocean.

An average kuo-toa stands roughly 5 feet tall and has a more or less humanoid appearance. Its rounded body is covered with fine scales giving it the appearance of being pudgy or bloated. The arms and legs are slender, almost willowy, ending in broad hands and distended feet that look very much like flippers. The bullet-shaped heads are piscene, with bulging, silver-black eyes and wide mouths full of needle-sharp teeth. Although kuo-toas are generally a silver-gray colour, their pigmentation changes with their mood. An angry kuo-toa is dark red, while a frightened one becomes pale gray or even white. The air around a kuo-toa carries the almost overwhelming odour of rotting fish.

Kuo-toa are an obvious choice as allies for the aboleths for many reasons. First, they are individually much weaker than the aboleths and can be bullied into servitude. Second, they are amphibious and can carry out their masters' plans on the surface. The aboleths keep the kuo-toa docile with their enslavement powers, but favoured kuo-toa leaders are allowed to keep their own minds as a reward for good service. Since most of the other kuo-toas remain enslaved, the aboleths have no fear that the few free-willed kuo-toas can engender rebellion.

Although most people shun contact with these loathsome creatures, sometimes avoiding them is simply not possible. Kuo-toa know much about long forgotten, ancient evils dwelling in the deepest parts of the ocean.

An average kuo-toa stands roughly 5 feet tall and has a more or less humanoid appearance. Its rounded body is covered with fine scales giving it the appearance of being pudgy or bloated. The arms and legs are slender, almost willowy, ending in broad hands and distended feet that look very much like flippers. The bullet-shaped heads are piscine, with bulging, silver-black eyes and wide mouths full of needle-sharp teeth. Although kuo-toas are generally a silver-gray colour, their pigmentation changes with their mood. An angry kuo-toa is dark red, while a frightened one becomes pale gray or even white. The air around a kuo-toa carries the almost overwhelming odour of rotting fish.

Kuo-toa are an obvious choice as allies for the aboleths for many reasons. First, they are individually much weaker than the aboleths and can be bullied into servitude. Second, they are amphibious and can carry out their masters' plans on the surface. The aboleths keep the kuo-toa docile with their enslavement powers, but favoured kuo-toa leaders are allowed to keep their own minds as a reward for good service. Since most of the other kuo-toas remain enslaved, the aboleths have no fear that the few free-willed kuo-toas can engender rebellion.

A crystal ooze attacks with sudden speed, flailing with its pseudopod to attempt to paralyse its victims. The ooze flows over paralysed victims to envelop and devour them.

No two phanes have exactly the same appearance, but all are shadowy and insubstantial. Though it is difficult to pierce the pale shadow of their form, some are vaguely humanoid, all are somewhat bestial, and many are downright nonhumanoid. Usually, two (sometimes more) emerald eyes burn from their shadowy form. Consisting of coalescent mist, the air ripples around the phane, and though it moves with feline grace, it seems as though it can barely hold itself together.

Phanes are not so much captive as lost so far in the past (or future) that time itself is without meaning. However, sometimes a phane escapes into the four dimensions of our multiverse. Here, phanes particularly enjoy collecting victims by permanently locking them in temporal stasis. Phanes can feed off the essence of creatures they temporally trap in this fashion. Other phanes are more ambitious, and seek to alter the fate of nations, worlds, and planes - for the worse. Phanes can manipulate time, which they don't hesitate to use to sow chaos among mortals. Occasionally they form pacts with powerful beings that share their destructive propensities.

Nothing is known of mu spore society, if any exists, and they appear to be solitary and highly territorial, driven by their constant need to feed. They have no need of others of their kind to reproduce. They are extremely cunning and deceptive as predators, and are able to speak common, so they will often enter into agreements with prey, in order to lure still more prey to their lairs before betraying the agreement and devouring all other parties involved.

The origins of the mu spore are also a complete mystery. Rumours abound, however, ranging from demented magical experiments on treants to extra-dimensional birth.

Dream larva are night terrors who escape dream into the waking world, nightmares made manifest. They have no specific form, but instead are every creature’s worst nightmare—each observer sees a dream larva for the first time as the most fearsome, terrible creature imaginable.

Dream larva have horns, a cruelly fanged mouth, four arms ending in claws, and four in pincers. No one knows how many dream larva infest the various regions of dreams. Most sleepers never dream the forbidden dreams that send their thoughts into the self-perpetuating nightmares that conceal and trap individual dream larvae. Such forbidden dreams are normally only triggered by the discovery of certain banned, divine manuscripts that have been mostly purged from the multiverse. However, sometimes dream larvae are disturbed nonetheless (or purposefully summoned). When they are, they follow the dreamer back into the waking world, and attempt to plunge all of creation into a true nightmare of their own creation.

A ruin swarm appears as an amorphous, mutable cloud of darkness like billows of smoke marking a scene of destruction. A swarm emits a thunderous roar that can be heard as a rumbling drone from up to a mile away. As the swarm moves through the water, its shape constantly spirals, twists, and mutates, and sometimes even divides into two or more distinct units before rejoining again moments later.

A ruin swarm originates in areas of magical contamination or leakage, or possibly through the design of an arcane experimentalist. Once formed, a ruin swarm is for all intents and purposes a single organism of the ooze type - its individual particulates have no more bearing on its vulnerabilities or powers.

A ruin swarm possesses vestigial intelligence but speaks no languages.