Kin

The Kin. Children of Old leech. Shape-shifting maneaters of lore.“For they were the stuff of nightmares; maggoty abominations possessed of incalculable and vile intellect that donned flesh and spines of men and beasts to shield themselves from the sun and enable themselves to walk upright instead of merely slithering.” They hunt humans, and they have very particular tastes. With the benefit of hindsight, we can see the pattern start to emerge in the earliest stories. There is something about the brain which has been through an emotionally taxing experience that lends it a flavour which they find delightful. The more such experiences the better. (They also eat children, yes, but I suspect that they do so primarily because of its impact on the witnesses and survivors. You can season an entire community with one little bite.)
The Kin are terrifying horrors from the outer dark not to be taken lightly at all.

“The nethermost caverns, are not for the fathoming of eyes that see; for their marvels are strange and terrific.  Great holes secretly are digged where earth’s pores ought to suffice, and things have learnt to walk that ought to crawl.”
What were they? Breeding grounds, feeding grounds, shrines? Or something utterly alien, something utterly incomprehensible to match the blighted fascination that dragged me ever closer and consumed my will to flee.

"There are things to be frightened of in that picture. Enlightenment isn't necessarily a clean process. Enlightenment can be filthy, degenerate, dangerous. Enlightenment is its own reward, its own punishment. You begin to see so much more. And so much more sees you."
The only thing an advanced species would want from us would be our meat and bones." "Hey." The voice floated from the thicker shadows of the alley. It was a husky voice, its sex muted by the acoustics of the brick and stone. "Hey, mister." A low, wheezy chuckle accompanied this.
Wylan dragged on his pipe and peered into the darkness. The muscles in his neck and shoulders bunched. His hand shook. He opened his mouth to answer that odd, muffled voice and could not speak. His throat was too tight. What did it remind him of? Something bad, something tickling the periphery of his consciousness, a warning. A certain quality of the voice, its inflection and cadence, harkened recollections of hunting for Cougar in the high grass in the lowlands, of chopping like through the Southern jungles on the trail of deadly quarry—of being hunted.

"Mister." The voice was close now. "I can see you. Please.

I hallucinated that Royce caused a window to open in the bedroom wall, a portal into space. Boggling! Millions of stars blazed inches from my nose, a whole colossal bell-shaped galaxy of exploded gases and cosmic dust. The sight would've driven a mage insane. It was a trick, stage magic. Something he'd borrowed from his fellow performers. He asked me what I saw and I told him. His face . . .there was something wrong. Too rigid, too cold. For a moment, I thought he'd put on an extremely clever mask and I was terrified. And his mouth . . .His expression melted almost instantly, and he was just Royce again. I knew better, though. And, unfortunately, my fascination intensified.