A spacefaring species of red, amphibious humanoids which come from - as they put it: "the star system you call Scorpius". They're a hostile civilization, which has invaded and took over several planets in the past.
This species is born from enormous eggs, about 6 ft in length, and hatch from the eggs as already fully-matured adults. The colony established on Earth uses an uncharted island as a hatchery containing millions of such eggs. Under normal conditions, these eggs can take centuries to hatch, but nuclear radiation can speed up the process considerably.
Their technology is based on something they refer to as "force rays", and allows them to display several abilities, such as paralyzing people, teleporting objects over great distances and even cloaking an entire island, making it appear invisible and undetectable.
In the early 1980s, aliens of this species were observed over the course of five weeks in the vicinity of an uncharted island which they used as a hatchery. When the SSRN Seaview started to investigate they came across the aliens, who attempted to sink the submarine and use its nuclear reactor core to speed up the development rate of their eggs and create a full-scale army to take over the world. They're ultimately obliterated as the Seaview bombards the island with missiles, saving the Earth as a result.
- Voyage to the Bottom of the Sea, s03e23 - "Doomsday Island" (1967)
- The aliens claim that they hail from "the star system you call Scorpius". In real life, there isn't any star system with that name, so it's possible that the alien was actually referring to the constellation of Scorpius.
- The fact that they can travel through space but seemingly can't develop nuclear reactors on their own suggests that their technology operates on highly different principles from ours. This is consistent with the mysterious nature of what they refer to as "force rays".