|Ted Nasmith's illustration of Lúthien and Beren disguised as Thuringwethil and Draugluin|
Thuringwethil (Sindarin: the 'Woman of Secret Shadow') was a vampire messenger of Sauron, who possessed bat-like wings which were barbed with an iron claw at each joint, and who carried out his errands between Angband and Tol-in-Gaurhoth. Little is known about her, but it has been indicated that she may have been a lesser Maia, perhaps brought into service by Melkor. While she is associated with vampires, she merely takes on their form; she is not explicitly referred to as being a vampire.
She was caught in Tol-in-Gaurhoth and her winged form was taken from her by Lúthien, who used Thuringwethil's shape to enter Angband with Beren, where the stole one of the Three Jewels (Silmarils) from Morgoth's crown and achieved the Quest of the Silmaril.