Hailing from the depths of Fluidic Space, Species 8472 were an invading cosmic horror few Captains other than Kathryn Janeway could have successfully faced down.
Even the Borg were terrified of them, so much so that they did the unthinkable and asked the crew of the Voyager for help. This formed one of the most controversial and disturbing alliances Star Trek has ever seen.
With a simple message for everybody living in the Milky Way — “the weak will perish” — Species 8472 represented the apex of biological evolution. They were notoriously hard to kill, and their weapons could smash through a Borg cube with the same ease that a photon torpedo could tear through Neelix’s Talaxian freighter.
As individuals, they were immensely strong, needed no atmosphere for breathing, and could rip human limbs off with limited effort. Their DNA was of a triple helix structure, and each cell contained one hundred times the DNA of a human cell. The species also appeared to have as many as five distinct sexes. Their powerful immune systems rendered them impervious to Borg assimilation. On top of all this, they were telepathic, able to speak to each other using only their minds.
Relations with the Federation
Unlike the Borg, they were also capable of hatred, and quickly came to see Voyager and humanity as their greatest threat, thanks to Janeway and her crew developing bio-molecular warheads (using Borg nanoprobes) capable of defeating Species 8472’s ships. When Voyager was trapped in Fluidic Space, they were forced to destroy several pursuing vessels during their escape, drawing the ire and fear of Species 8472.
Species 8472 could genetically modify their bodies to mimic other lifeforms – even humans. Some time after their initial encounter with the species, Voyager discovered Terrasphere 8, a perfect recreation of Starfleet Academy, complete with mimicked Starfleet officers, right down to the Academy groundskeeper. This base was being used as a training camp by members of Species 8472 in preparation to infiltrate and annihilate the Federation. While other Captains may have destroyed the facility, Janeway instead managed to establish communications with Species 8472, and brokered a ceasefire with them in exchange for the technology used to design the bio-molecular warheads. Voyager and 8472 therefore parted on amicable terms.
Despite returning to Fluidic Space with a newfound respect for the Federation, Species 8472 remains a worrying presence in the wider Star Trek universe. With so many new Trek series in production, it is quite possible that the one enemy the Borg feared could make a deadly reappearance.