I actually own this movie which is the MST3K version called "Cave Dwellers" which is really the only way anyone could really watch a movie like this. If it weren't for Joel, Crow, and Tom Servo constantly making wisecracks, it wouldn't be possible to sit through this piece of crap. You have a hero called Ator who looks a lot like Jeff Spigoli in Fast Times at Ridgemont High and appears only slightly more intelligent, just without being stoned. He takes on cavemen (the cave dwellers?) invisible guys, a giant snake (with a bunch of anal retentive snakes that like to line up all the skulls to face the same way), invents a hang glider which suspiciously looks like a modern aluminum one with some cheap vines wrapped around it, and then does battle with the evil John Saxon-looking dude. Then he rides off on his horse across the tire tracks where someone's been four-wheeling.
Yes, I got most of that from MST3K, which as I said is the only way to watch this turkey of a movie. If it weren't for that, it would get zero stars.