Star Trek: 10 Strangest Alien Species
1. Species 8472
When it comes to alien species in Star Trek, this is about as strange as it gets, especially when you consider this species regularly laid a whoopin' on the Borg.
Species 8472 was the Borg designation for an alien race that lived in fluidic space, an extra-dimensional realm filled with organic fluid and apparently no celestial bodies. The Borg gained access to fluidic space through a quantum singularity and attempted to assimilate Species 8472. It did not go well. 8472 proved to be tactically superior to the Borg and invulnerable to the assimilation process.
Their war spilled out into normal space, with the Borg on the losing end of the conflict. Then, Voyager stepped in and turned the tides in the Borg's favor. While a war with the Federation seemed imminent, the crew of the Voyager was able to convince 8472 otherwise. After a peaceful exchange of information, Species 8472 returned to fluidic space.
No other name than Species 8472 was ever discovered so the Borg designation was used by the Federation. The fact that they were so dominant over the Borg makes them incredibly unique, and more than a little scary. If the Borg ever try to take the Federation down, again, Janeway should consider opening a singularity and unleashing hell.