‘Again the withered hag poured forth the monotonous words of a prayer that was not meant to be acceptable in Heaven; and soon, in the pauses of her breath, strange murmurings began to thicken, gradually increasing so as to drown and overpower the charm by which they grew. Shrieks pierced through the obscurity of sound, and were succeeded by the singing of sweet female voices, which in their turn gave way to a wild roar of laughter, broken suddenly by groanings and sobs, forming altogether a ghastly confusion of terror and mourning and mirth.’

–NATHANIEL HAWTHORNE (The Hollow of the Three Hills)

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The screams, that fourteenth night, continued until dawn. They were totally unlike any sounds in my experience. Impossible to believe they could be uttered and sustained by a human, yet they did not seem to be animal. I listened, there in the gloom, my hands balled into fists, and knew, suddenly, that one of two things must be true. Either someone or something was making these ghastly sounds, and Brother Christophorus was lying, or–I was going mad. Hearing-voices mad, climbing-walls and frothing mad. I’d have to find the answer: that I knew. And by myself.
–Charles Beaumont (THE HOWLING MAN)

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Dim, dubious, bat-like creatures seemed to be flitting to and fro between one of the stone vats and the group that toiled like sculptors, clothing the bony foot with a reddish plasm which they applied and moulded like so much clay. Gaspard thought, but was not certain later, that this plasm, which gleamed as if with mingled blood and fire, was being brought from the rosy-litten vat in vessels borne by the claws of the shadowy flying creatures. None of them, however, approached the other vat, whose wannish light was momently enfeebled, as if it were dying down. –Clark Ashton Smith (The Colossus of Ylourgne)

HIS voice came to us again. He said, at first, that he saw nothing in the abyss below him. Then he gasped, swayed, and almost lost his balance. We could see the sweat standing out on his brow and neck, soaking his blue shirt. There were things in the abyss, he said in hoarse tones, great shapes that were like blobs of utter blackness, yet which he knew to be alive. From the central masses of their beings he could see them shoot forth incredibly long, filamentine tentacles. They moved themselves forward and backward — horizontally, but could not move vertically, it seemed. They were, he thought, nothing but living shadows.
Robert A.W. Lowndes (THE ABYSS)