Beyond a doubt Species 8472 represents one of the most highly evolved and advanced life forms outside of the Q continuum. Their weaponry is far and away beyond anything that the Federation has experienced before; their relatively small bioships are more than capable of defeating Borg cubes one on one, while small groups can combine their fire and use it to destroy entire planets in seconds.

Species 8472 themselves originate from beyond our dimension. They came into contact with our galaxy when the Borg invaded their space in an attempt to assimilate their biological technology. The attempt failed, and species 8472 (the Borg designation for them) responded by invading our galaxy - apparently intent on utterly eradicating not only the Borg but all other species also.

The Borg were being heavily defeated by 8472 when the Intrepid class USS Voyager came across them; Voyager was able to modify Borg nanoprobes to analyse and attack the 8472 ships on the cellular level. Voyager was able to design warheads based on these nanoprobes, and in skirmishes with 8472 bioships was able to overcome and destroy them in numbers. Subsequently the 8472 invasion fleet has returned to their own dimension and has not returned.