This film opens with a woman running through woods (being chased by a mainly unseen being). This is never a good sign. If you've watched pretty much any handful of random horror films, you'll know that `woman running through woods' is possibly the most overused cliché of the genre (with perhaps the teenagers having sex and dying being a close second).
That opening is a kind of warning of things to come. Some films thrive on having a low budget. The lack of money behind the picture forces the film-makers to use new and more subtle techniques to tell the story. Not here. This film has no budget and it shows in every scene.
It's about a team of archaeologists, sent somewhere in South America (like the location really matters!) to retrieve something for someone (again, such details are kind of pointless in the scheme of things). However, this `South American' jungle looks suspiciously like some nice grassy fields in America. Plus the `natives' also look a little Caucasian, considering they are supposed to have lived in the hot jungle all their lives.
The acting isn't all bad, but the dialogue is. Just because the film is set in a wood (sorry, jungle), the writers seem to want to make the characters talk like they're out of Predator. Yes, there's something hunting them, but whereas Predator used a monster that was actually there, the makers of Mandrake spent the entire $2.50 budget on some `creepy' CGI tentacles. Woo.
If you like cheesy monster-munching movies, then you probably know plenty out there which will amuse and entertain (try things like Deep Rising, Tremors, or Grabbers to name but a few). Mandrake is not one of them.