Thale (2012)

Norwegian folklore turns out to be real when Leo and Elvis encounter a girl called Thale in a basement. A regular cleaning job turns into a struggle for survival, while they're trying to figure out what or who Thale is. Could Thale be a huldra? A seductive forest spirit who appears from the front to be a beautiful young woman, but who also has a cow's tale and whose back appears to be like a hollowed out tree. The huldra has been known to offer rewards to those who satisfy them sexually, while death to those who fail to do so and are also prone to stealing human babies.

Source: TMDb