The Loreley's Grasp

The legendary Lorelei has been living for centuries in a grotto beneath the Rhine river in Germany. Every night when the moon is full, she turns into a reptile-like creature craving for human blood. When one girl after another of a nearby boarding school is killed by her, a hunter named Sirgurd is engaged to kill the monster.

The Loreley's Grasp is a 1975 fantasy horror movie directed by Amando de Ossorio, starring Josefina Jartin, Tony Kendall, Helga Liné. It holds an IMDb rating of 5.7/10 from 1,156 votes and runs 1h 25m.