Four college kids are summoned to a remote cabin belonging to a nutty old professor (science fiction author Fritz Leiber, moonlighting between books) who, turns out, had his hands on a 1000-year-old demonology tome/early draft of the D&D Monster Manual and was practicing a little black magic in the name of science. Whoopsie. Also included with admission: a scaly, prehistoric boogeyman; disappearing castle; giant, cabin-crushing land octopus; possessed park ranger; vanishing corpses; creepy, cackling, cave-dwelling geezer; portal to evil dimension; devil-worshiping monks; doppelgangers; angry green homunculus; flying skull-faced devil (Asmodeus himself). Be sure to make your saving throw vs. insanity, or risk being stunned for 2-4 rounds.
Quintessential amateur low-budget horror schlock, ripe with stop-motion creatures and the worst ADR dubbing you'll see/hear this side of Toho Studios. Originally a student film (credit: Dennis Muren and Mark Thomas McGee) cobbled together on a $7K budget, later purchased by filmmaker Jack Woods who assumed director's credit after editing in footage of his own, meant to expand the story (and create a role for himself) but resulting mainly in goofy continuity errors. Both versions are silly fun; the shorter 1967 cut makes marginally more sense. Featuring a pre-WKRP in Cincinnati Frank Bonner, young but already heading into Herb Tarlek mode. Ed Begley Jr. served as assistant cameraman for the 1970 pickup shots. Sam Raimi lifted the basic plot elements for Evil Dead (1981).