Neh-thalggu

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Brain collectors, or neh-thalggu in their own language, were a race of creatures found across multiple planes.

Description
Juvenile neh-thalggu were about with six crab-like legs and dozens of short tentacles. They had yellow-orange skin and a bloated, almost amorphous body. The head area of the body had four yellow eyes and a large, tooth-filled maw. Additionally, a brain collector could have up to twelve lumps on its head, which contained the brains it had collected.

Adult neh-thalggu were much larger and had more legs, typically twelve but some could have as many as eighteen or even twenty-four legs. Additionally, they possessed a thirteenth lump on the head that could hold an extra brain.

Abilities
Neh-thalggu were highly intelligent, and were also capable spellcasters. The amount of spells they could cast depended on the number of brains one had collected. The more brains a juvenile had, the more spells it knew. For adults, the number of brains dictated both the number and power level of spells they knew. Neh-thalggu also drew upon any knowledge held by the brains they absorbed.

As juveniles, neh-thalggu could cast spells of up 3rd level. They could also enhance their spells in one of three ways by absorbing a brain, allowing one to either cast a spell without using somatic or verbal components, increase the range of a touch spell to up to, or cast a spell while biting another creature, although the last had a chance to fail if the creature managed to evade the bite.

As adults, neh-thalggu were much more dangerous. They became incorporeal, could cast more and more powerful spells, and could use dimension door, teleport without error, and plane shift at will. They could also remove the brain from any creature they could see by extradimensional means (a dimensional anchor spell could block this effect). Their bite became venomous, injecting a debilitating poison into victims. A single hit from the whip-like tentacles on the head could dehydrate someone.

Neh-thalggu spoke their own language, which was a silent one consisting of the movement of their tentacles, as well as Diabolan, the language of the diaboli. They also could speak any language spoken by someone whose brain they had taken. Juvenile neh-thalggu possessed telepathy with a range of, while fully grown adults had a telepathic range of.

Neh-thalggu possessed an alien physiology that constantly shifted and changed within them. This rendered them immune to both disease and poison.

Personality
Brain collectors possessed a completely alien psychology: while not exactly hostile, they did not regard humanoids as people, only as food. They had no interest in wealth, power, magic, or other pursuits common to most species.

Combat
In combat, neh-thalggu relied on their powerful jaws and their spellcasting ability, and displayed considerable tactical ability due to their high intellect. Interestingly, they would take great care to avoid damaging the cranium of their opponents.

Society
Neh-thalggu were solitary creatures known to live on the Material plane, Astral plane, Ethereal plane, and the Demiplane of Nightmares. On the first in particular they were known to prefer ruins or caverns where there was little light and minimal disturbances. However, the homeplane of the neh-thalggu was unknown, though it was speculated to be some strange demiplane in the Ethereal or a bizarre Material plane, or even a plane that had been destroyed long ago. Other reports claimed the neh-thalggu came from the Far Realm.

Juvenile brain collectors always sought to acquire brains as quickly as possible, and did so by carefully cutting off the top of the head of a slain humanoid using surgical tools, then swallowing the brain. Once one had collected twelve brains, it immediately sought to return to its home plane. According to one theory, a twelve-brain neh-thalggu could open a link to its native plane when in a certain location, while other records stated that when a neh-thalggu acquired twelve brains it could potentially transform from a juvenile into an adult.

On the Demiplane of Nightmares, neh-thalggu occupied a place in diabolus legends similar to the one dragons held in human legends. Diaboli regarded neh-thalggu as creatures of great power, cunning, and inscrutability. Additionally, neh-thalggu were some of the few creatures whose magic could affect a diabolus.

Neh-thalggu were known to go to the Astral plane to rest and recover from their activities on the Material plane, and so did not often hunt while there. However, when they did fight in the Astral plane, they still took the brains of fallen opponents.

Adult neh-thalggu were sometimes accompanied by up 5 mind flayers or, more rarely, a single paragon mind flayer. Normal mind flayers were drawn by and would study the neh-thalggu's ability to collect brains and how it used them in arcane casting. The exact nature of the relationship between a neh-thalggu and such followers was unknown, but theories about it ranged from simple self-interest to something close to worship on the part of the mind flayers. Neh-thalggu would pass along brains they collected but did not want to keep to the mind flayers.