A "Planet of No Return" type of yarn--cosmonaut goes to tribal age planet and once his base is overrun by treacherous primitives, is forced to go all Conan on their asses while trying to figure out the planet's central mystery.
By any reasonable standard, a terrible, terrible film. However, if you belong to the tribe of perverts who spasm in joy from 1980's Italian no-budget Conan, Star Wars, and Mad Max knockoffs, then this 1980's Soviet Conan and Star Wars knockoff will knock your socks off.
While the acting quality and special effects are absolutely identical to those in say Ator The Fighting Eagle , or Star Odyssey , the differences are two: a) the main characters are obviously Slavic, be they earthling or local, while the baddies are darkly stubbled and speak in pseudo-Arabic throaty croaks, and b) the film is actually based on a real (and quite good) science fiction book.
Unlike the Italian (or no-budget American) brethren of this film, where the plot is held together with spit and gum, the plot in The Witches Cave actually makes perfect sense and is none too shabby, because it follows the aforementioned science fiction novel.
This is scant relief for those who expect mainstream entertainment from this film (they will not get it), but by a measurement scale of bad B film lovers of the 1980's Italian, or Roger Corman type of cinematic adventure, this is a solid "8 out of 10" flick.
Summary: The Witches Cave is a very good choice for all connoisseurs of cheap 1980's fantasy and sci-fi, with the two added bonuses of the film's exotic component (Soviet), and the plot being an actual functioning such, due to being based on actual book.
