Thuringwethil

Thuringwethil (Woman of the Secret Shadow) is a fictional character in J. R. R. Tolkien's Middle-earth legendarium. Her hide was used as Lúthien's disguise when she entered Angband on the Quest of the Silmaril. 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.