Gorgo #12

Huge cyclopian octopus creatures from Venus land on a small island to set up a base. These creatures plan to study humanity so they can learn how to conquer Earth. They do so by sending out their shapshifting minions to kidnap scientists. After they learn how unimpressive humans are, they call in their invasion forces. They never counted on giant monsters though, as Gorgo, his mother, and Reptisaurus all show up to destroy them.