A plumard is a vampire-like monster mentioned in the ancient tome used by the old wise woman of Lower Posada in the short story "The Edge of the World".
“
—though the witchman greatly covetous and greedy for gold be, mumbled the old woman, half-closing her eyes, giveth ye not such a one more than: for a drowner, one silver penny or three halves; for a werecat, silver pennies two; for a plumard, silver pennies—
”
— pg(s). 180, The Last Wish (UK edition)