Mindflayers

This post has been a long time coming, inspired by Bargain Bin Mindflayers on the titorpg blog (who incidentally wrote a Weird & Wonderful Appreciation post). I take the idea very loosely, most of these are pretty distinct from typical mindflayers and could be included right alongside them. They're powerful, eldritch beings inspired primarily by weird sea life.

Protean Proselytizers

Sea Angels

Smooth, semi-translucent, white, winged creatures that stand over 7' tall and emanate bioluminescence; like bio-droids designed by Gothic architects and Apple. They enslave gods and bend their divine powers to their will. They travel the planes, looking for worlds with vulnerable or neglectful gods, and convert the people and usurp the gods with specifically-crafted cults leveraging the abilities of their legions of enslaved gods.

Psychedelic Stingers

Jellyfish

Semi-amorphous, whispy, tentacled beings that float between dimensions. No two look alike, with various shapes, degrees of opacity, and forms of bioluminescence. They are ancient beyond time itself, able to hibernate and rebirth themselves in the null-space between dimensions. They will latch their stinging tentacles and attach their bulbous forms onto mortals, usually over their heads, and operate their bodies like machines, in order to function on mortal planes. They attach more easily to the dead, and so they often appear in hordes after battles, plagues, and exterminations.

Vorpal Vivisectionists

Horseshoe Crabs
Some unfortunate warriors who die at sea are harvested by unknown deep-sea gods of the abyss and are brought back in undeath covered in chitin. They follow the code of anti-bushido, and gain greater necromantic power with every mortal kill, especially by the slicing and stabbing of the brain. These anti-samurai are intelligent, but soulless. Their purpose is violence, destruction, and conquest, seemingly for its own sake. It is thought that their souls are stored in caviar-like eggs somewhere in the abyss, making them liches.

Cerebrospinal Sharpshooters

Mantis Shrimp

Colorful chitinous creatures with stalk-eyes and magical claws. They see the samsara cycle with their circular polarized hyperlight vision, and the raw, recursive nature of the numerous numinous dimensions has driven them mad, or perhaps hyper-sane. They seek to destroy all; through brute force, smashing with their claws, volleyed at superspeed with the power of sonic booms, or by clicking their claws, producing pistol-shot waves of psychic force.

Luciferous Lamia

Anglerfish

These demons exist on higher dimensions, propagating in mortal spacetime by way of a bioluminescent appendage. The spacetime bulb produces a light distortion, a hologram, projecting just above spacetime, such that the hologram is like a four-dimensional (space + time) shadow. The holograms are always beautiful and magically alluring, but these beings are pure predators. Although the holograms take many forms, the Luciferous Lamia are themselves always female; the males are significantly less powerful, incapable of holographic projection, and merely latch to the females for survival (until they are absorbed into them).

Mutant Megadeath Mindflayers

Vampire Squids

These beings from a psionic infernal plane are to mindflayers as demons are to humans. Black and red-skinned, usually humanoid cephalopods with striking, flashing bioluminescence. They are vampires who feed on the mental energies of mortals, especially "hot" energies like hate and anger. Their infernal dimension is a plane of thought, a kind of volatile, explosive psionic space. Unlike the slender illithid, they tend to have hulking, muscular bodies. Whereas illithid experiment on and enslave other creatures, mutant megadeath mindflayers empower and mutate themselves off the hateful energies of other creatures. A single one of their kind can single-handedly slaughter an entire company of illithid, projecting balls, beams, and blasts of infernal psionic energy greater than nuclear blasts; in some cases, great enough to destroy whole regions of celestial space in a single blow.