The Keep (1983)

From IMDB: Tagline: THEY WERE ALL DRAWN TO THE KEEP. The soldiers who brought death. The father and daughter fighting for life. The people who have always feared it. And the one man who knows its secret... THE KEEP Tonight, they will all face the evil. Plot Outline: Nazis are sent to guard an old, mysterious fortress in a Romanian pass. One of them mistakenly releases an unknown force trapped within the walls. A mysterious stranger senses this from his home in Greece and travels to the keep to vanquish the force. As soldiers are killed, a Jewish man and his daughter (who are both knowledgable of the keep) are brought in to find out what is happening.