The Keep (1983)
Synopsis: Nazis are forced to turn to a historian for help in battling an ancient demon they have inadvertently freed from its prison.
Starring: Scott Glenn, Ian McKellen, Gabriel Byrne, Jürgen Prochnow
You would think with a cast of actors such as these that this movie would be good. Well, you'd be wrong. This film makes The Sword and the Sorcerer look Oscar worthy.
I think this looks like a good movie, but I know it get absolutely no exposure so I'll back you up.