Hey wiseagent! I recently watched this movie, it's free on YouTube by the way, and I loved it from beginning to end. I agree with you, the practical effects gave these 80s movies a unique identity, and considering how complicated it is to adapt a Lovecraftian work, it's very impressive. I'm going to watch Possession (1981) soon; I understand that the person behind the effects was Carlos Rambaldi, the same person behind the effects for Alien (1979). Regards!
!BBH