Burnt Offerings (1976)

What is it with haunted house movies from the late 70's-early 80's, anyway? It seems that, without a single exception, they're always awesome - awesome cinematography, awesome casting, awesome atmosphere, etc. In addition, they always seem to feature some hidden or isolated room which the supernatural presence seems to use as its base of operations; that's always, always a cool motif that never loses its effectiveness.

And may I just add that this guy

is the perfect stuff of nightmares.