The Rats in the Walls

I retired early, being very sleepy, but was harassed by dreams of the most horrible sort. I seemed to be looking down fom an immense height upon a twilit grotto, knee-deep with filth, where a white-bearded daemon swineherd droe about with his staff a flock of fungous, flabby beasts whose appearance filled me with unutterabe loathing. Then, as the swineherd paused and nodded over his task, a mighty swarm of rats rained down on the stinking abyss and fell to devouring beasts and man alike.

(the beasts later turn out to be a subhuman species that the narrator's forefathers herded underground and canabalistically ate like cattle)