Passable scifi with a solid cast and one of the worst monsters I’ve ever seen. Lee Van Cleef in an early major role is solid, as is Peter Graves, and the acting quality is fine, and it was reasonably entertaining except for (a) a ridiculous monster, and (b) one of the worst closing monologues I’ve ever heard.
It was redeemed somewhat by the graphic, exploitation death of the monster though. I also liked the flying bat/skin-pizza monsters the alien sent out to control people – that reminded me of similar beasties in original series Star Trek.