Frisian Terror.

In the late 80's, a Russian general orders a search party to find a skull with supernatural powers in the Dutch forests which belonged to a Frisian medieval King. The skull is found and a famous archaeologist gets possessed by it and turns into the kings faithful prophet A couple of years later the prophet - who is now leader of a bloodthirsty cult which includes his beautiful girlfriend and family - kills and tortures in the name of the 'Almighty King Sigurd'.