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Thuringwethil (Woman of the Secret Shadow) is a character in J. R. R. Tolkien's Middle-earth mythology who appears in The Silmarillion. Thuringwethil was a vampire messenger of Sauron, probably a Maia, who took the shape of a bat-like creature. Her wings were barbed with an iron claw at each joint. Her hide was used as Lúthien's disguise when she entered Angband on the Quest of the Silmaril.