Ecology of the Cult of Cthulhu

Since mind flayers are product identity, I decided to replace them with some open content substitutes. The Cult of Cthulhu are the offspring and avatars of the Great Old One Cthulhu. All of the various freaky psychic tentacle monsters from monster manuals, bestiaries and third party products are different varieties of the Cult. UPDATED 10/30/2017

Phrenic Scourge ©2005 Beth Trott

Nomenclature: aboleth, alghollthu, brain lasher, children of the Outer Gods, chthonoid, lethid, mind eater, moon beasts, neothelid, othagu, phrenic scourge, possessor, psycholus, star spawn of Cthulhu, thelidu, thulid, and many more

Description: tentacle monsters with psychic powers, love enslaving humanoids, create weird monsters, etc; otherwise come in a truly dizzying variety with little in common other than a general seafood aesthetic

The Cult originally entered the world when Cthulhu tried to travel there from the planes of discord. His bulk was so vast that he seemed more like a vast swarm of aberrations rather than a single entity. When these resulting children and avatars manifested for the first time, the universe found them (like other aberrations) so abhorrent that it cloaked their mind-blowing true forms in flesh that mimicked deep sea fish, crustaceans and mollusks. Since then, the Cult devised numerous means of propagating their kind without summoning more immigrants from the planes of discord.

It is impossible to give a general description of the Cult due to their sheer diversity as immigrants from the planes of discord. They include brain parasites, deep sea fish, masses of tentacles, half-human hybrids, and so much more. What is possible is giving a limited account of creatures which have been encountered before.

• Phrenic Hegemony: the phrenic scourges are your classic hideous tentacle monsters. They incubate their ravenous larvae inside the bodies of other creatures. This process has occasionally resulted in mutated scourges which were refined into servant races.
• Puppet Masters: known by names like possessor, puppeteer and lethid, the brain parasites take over the bodies of other creatures to make up for their lack of physical might. Their small appearances are quite variable: ticks, slugs, rays, head-eating cephalopods and so forth.
• Deep Ones: known by names like aboleth, alghollthu and othagu, the deep ones include creatures which resemble deep sea fish. They have devised many methods of quickly creating half-human hybrids like abollar, gillmen and skum. Compared to other varieties, they are more likely to recruit willing humanoids into cults rather than outright enslave them.
• Burrowers Beneath: the burrowers are gigantic mollusks which primarily lair in the Underworld. They include some of the largest and most dangerous varieties ever encountered, such as the neothelid and undermind.

The Cult once came into conflict with the Empire of Atlantis. The empire was shattered, the saurian rulers were scattered, and many human survivors were enslaved and transformed into gillmen. Even so, their sacrifice prevented the Cult from taking over the world at the time.

The Cult is supposedly responsible for creating many of the monster that bedevil dungeons, such as lurking rays (including the cloaker, cuero, executioner’s hood, lurker above, lurker below, and trapper), lurking cephalopods (including the darkmantle, decapus, and tentamort), lurking gastropods (including the delver, piercer and roper), metamorphs (including, doppelgangers, mimics, and doppelstadte), and shoggoths (from who descend the gibbering mouthers, black puddings and other blob monsters).

They use a variety of freakish, vaguely living arms, armor and tools for their innumerable experiments and skirmishes. Similar tools have been found in the possession of races which commonly contact the Cult, presumably traded or stolen.

The Cult sometimes exhibit sectarian violence over the "right" way to worship Cthulhu. This has sometimes tricked other races into believing that the sects are actually different races involved in a race war. In fact, many sages still have difficulty believing that all these creatures are merely parts of a greater whole.

Suggested Resources: Forgotten Foes, High Psionics: Phrenic Scourges, The Iconic Bestiary: Classics of Fantasy, Monster Encyclopaedia series, Monster Menagerie: Horrors of the Aboleth, Monsters of Porphyra series, Pathfinder Bestiary series, Possessors: Children of the Outer Gods, Slavelords of Cydonia, Psionic Bestiary, Unveiled Masters: the Essential Guide to Mind Flayers.