Anguiliian

Anguiliians, sometimes spelled anguillians, were oceanic predators related to the sahuagin. They were also called heumixumlis by merfolk, a term that literally translated to "eel man from the deep".

Description
Anguiliians had eel-like bodies with relatively small heads, large eyes, and broad, ear-like fins on the side of the head. Their mouths were round and full of many rows of sharp teeth. Unlike the closely related sahuagin, however, they possessed only rudimentary limbs, with shorter, although very similar, legs that ended in six clawed and webbed toes. Their arms were more different, ending in pincers. The skin was muddy brown with dots or speckles of black and tan.

Personality
Anguiliians were as evil, if a little less regimented than, their sahuagin kin. Status within a tribe was determined by strength.

Abilities
Anguiliians were fast and agile swimmers who could see in complete darkness, but were blinded by bright light. They were capable of surviving on land only for a short time before drowning. They were immune to electrical damage but were vulnerable to fire. They also possessed similar intelligence and memory abilities, and the same hypersensitive senses as sahuagin. They were also sensitive to fresh water in the same way.

Anguiliians could communicate simple concepts to eels and dire eels within of them, and were known to train the creatures. Among themselves and with other creatures, they spoke a dialect of the sahuagin language.

Combat
When fighting, anguiliians preferred to form a loose sphere around their target, with some attacking from above and all sides, and most attacking from below. They darted in and out, attacking with their teeth, pincers, and tail. Their pincers were capable of crushing shell and bone, and could slice flesh easily. More disturbingly, an anguiliian that successfully bit an enemy could attach themself to it and drill inside of it, or drain the liquids out of it. They had been known to eat larger creatures inside out in this way.

They were known to carry crude spears in their pincers.

Society
Anguiliians lived in the open ocean at depths between. They formed free-swimming tribes that remained in motion near-constantly, with females carrying eggs as they swam. Tribes were patriarchal, ruled by an older high chieftain who presided over numerous lesser chieftains that held more administrative positions, and subchiefs, who led hunting parties. Chiefs were often challenged by younger males. Unlike their cousins, they lacked a regimented system of nobility or a priesthood.

Anguiliians were carnivores who would eat nearly anything, up to and including their own dead. They typically hunted all manner of fish, giant squid, and whales. Larger predators of the deeps such as massive sharks and krakens were known to prey on anguiliians in turn. When anguiliians rose to the surface, they only did so only on moonless nights to avoid the unfamiliar light.

Anguiliians were known to sometimes trade items scavenged from shipwrecks to sahuagin in exchange for useful tools like nets and poisons. The sahuagin, for their part, probably would have driven the anguiliians to extinction long ago if not for the fact that the two races did not dwell in the same environments, and that not even sahuagin liked the taste of anguiliian flesh.

Anguiliians possessed similar internal physiology to sahuagin, with a major difference in that their skeleton was cartilaginous rather than bony; this meant that they could get through any opening that one could fit its head through.

Anguiliians were known to live in the Sea of Fallen Stars, and others were known to have gotten into flooded Underdark tunnels from deep-sea openings.

History
Scholars speculated that anguiliians were created at roughly the same time as sahuagin as part of an experiment aimed at created an evil race of aquatic humanoids. The sahuagin were the more successful and numerous half of the experiment, though the rare anguiliians managed to survive as well.

However, the truth was more complex. Long ago, before the sahuagin existed, before the elves had their great schism and some fled below the waves to become aquatic elves, a cabal of elves sought to adapt their kind to life in the ocean. Unwilling to wait to adapt naturally, they felt that arcanamorphosis (a magically instigated change that would thereafter breed true from one generation to the next) was the best option.

As they investigated and searched the sea, one faction of this cabal, called the Adherents of Vitality, discovered the undersea civilization of the anguiliians, who were at that time a highly advanced civilization that relied on half-living technology that was empowered by their deity. This civilization was led by their deity, Anguileusis, through the rulers of their civilization, who were called the Deep Father and the Deep Mother.

Anguileusis was so invested in the prosperity of his followers that he sought to leave the Outer Planes and join them fully in the form of a living anguiliian. To this end, he instructed the Deep Father and Deep Mother in a complex ritual that would draw his essence into an unhatched egg of theirs. Joyful at this prospect, the Deep Mother selected a perfect egg while the Deep Father created a compound below the sea floor wherein the ritual took place. The ceremony was successful, and the Deep Father held the hatchling-deity in his arms just as disaster struck.

The Adherents of Vitality, in their search of the ocean, had studied the anguiliians extensively. They were dismayed at the power of the anguiliians, for that evil species would be a serious threat to any sea colony of elves. When they discovered the upcoming ceremony, they knew that with a god-king at their head, the anguiliians would become a force that none under the sea could stand against.

However, the potential crisis also offered an opportunity. If the elves could neutralize Anguileusis, then the entire anguiliian species would be brought to its metaphorical knees. To that end, even as the ritual ended, the Adherents struck the compound with a force of truly powerful spellcasters, and used a painstakingly researched spell to turn the hatchling-deity and the Deep Father who held him to stone, creating an artifact called the Stone That Abides.

The Deep Mother survived and was forced to flee the compound, and in the aftermath, as their technology ceased to function, the anguiliian civilization collapsed as they reverted to hunting tribes. The attack of the Adherents had other lasting consequences, searing a distrust of arcane magic into their collective subconscious.

A few survivors swam upwards, seeking food in the more fertile shallows. Desperate and lonely, these anguiliians found the songs of the shark-god Sekolah. Sekolah, in turn, accepted those anguiliians as his followers. Their memories of Anguileusis were wiped by Sekolah, but the fear of arcane magic remained. As their minds changed, so did their bodies, and thus the sahuagin came to be.

Interestingly, sahuagin who much later reverted to worshiping Anguileusis were observed to exhibit some eel-like characteristics, raising the question of what effect did the worship of any given deity have on the physiology of the anguiliians and sahuagin.