Help finding old movie?

i need help on finding the name of this old movie that came on either showtime or cinemax and it looked like it was filmed in england or london or something all i know that the movie was and it was about a lady who who grew nails or fangs when she was having i remember one scene where she was having in a cave and her eyes went black and she started to grow nails and i believe the title could be called demon of the night or something like that