As old as the stars themselves, Gla'aki has a vast reservoir of knowledge, not only of the supernatural entities that exist on Earth, but of those which predate it. Whilst he is aquatic in nature, in his physical form Gla'aki resembles nothing so much as an enormous slug with slender spines which appear to be made of matte metal, but which are in fact organic in nature. These quills can inject a substance to ensure its victims' compliance. Those skewered in such a way are granted Gla'aki's gift of everlasting life, albeit as an undead puppet. In addition, it is capable of forming tentacles tipped with eyes, so as to keep its true nature hidden whilst observing the world from beneath the water's surface.
Gla'aki's cult, a group of depraved humans both mortal and undead, wrote a series of scriptures known as the Revelations of Gla'aki. What these writings contain is unknown, though it cannot be anything good.
The Green Decay
Those who have been infected by Gla'aki's foul fluid find themselves as nothing more than a sentient appendage of this vile creature. As time goes by, the body of the poor unfortunate degenerates to the stage where it can no longer act like a human being, and is physically harmed by the touch of daylight. This process is known as the Green Decay.
It is believed, by those who know of Gla'aki's existence, that in aeons past he had been imprisoned in a meteor by the Elder Gods. When the meteor finally fell to Earth, the monster was freed, and the resulting crater gradually filled with water, becoming the lake which Gla'aki now inhabits.
One story tells of an artist who sought solitude in a dwelling by the edge of Gla'aki's lake. The man discovered the writings of its cult in the basement, but was dragged off by the monster and his minions before he could escape to tell the world his tale. He was, however, able to break Gla'aki's quill before it could inject him with its fluid, thereby avoiding becoming one of its meat puppets, although this action ensured his speedy demise.
Sightings of Gla'aki in bodies of water across the globe are somewhat commonplace, though whether these reports are of the creature itself or merely a misidentified cryptid is anyone's guess.