The Nuckelavee is a sea-demon from the folklore of the Orkney Islands of Scotland, drawn as a horrifying figure: the body of a skinless horse fused with a human torso. Its breath alone is said to spread plague among livestock and crops.
Bodily revulsion at exposed sinew and vein layered over the dread of pestilence makes it one of the most visceral of the uncanny, sickening to behold by sight alone.