I remember this movie as a child. It terrified me even though I only saw about 10 minutes. There was a group of people at a mansion where a man had his head ripped off. There was this huge machine that when turned on these little squid creatures appeared. Reminded me of metroids almost. One guy got the shit bitten out of his arm. I remember turning the channel when this alligator creature showed up. It explained that the monsters were always there you and them just couldn't see each other. Sound familiar?