Vampire Hunter D - mutants
When I was a kid, there were only a few dubbed "Japanimation" films anyone had ever heard of. This included the original Vampire Hunter D, which used to play quite often on sci-fi channel and even once on Cartoon Network.
I love this sequence where D infiltrates the count's castle and is met with a huge horde of completely unearthly monsters. My favorites are the gelatinous, planktonic-looking things you can see floating around in a few scenes, and those wonderful lamprey-mouthed beasts. It's too bad they die so quickly.