Species 8472
In the fictional universe of Star Trek, "Species 8472" is the name (designated by the Borg) of an advanced alien race that lives in the realm of fluidic space.
Anatomy
They have a dense genetic structure with triple-helix DNA and a powerful immune system. Their anatomy is unique in that they possess three legs and communicate exclusively through telepathy. Apparently, their species is composed of five different genders, and each of the sexes own separate sections of the fluidic space realm in which they live.
Technology
Species 8472 possesses a biologically-engineered ship known as a bioship. This ship is capable of melting itself through various surfaces, like that of a Borg vessel or a starship. It is also capable of rapidly regenerating damaged systems. If the weapons of one bioship are linked with that of several others, they posses the ability to rapidly eliminate entire planets. Since the bio-ship has similar genetic make-up to its pilots, it is possible that species 8472 control their ships through telepathy.
History
Relevant episodes: Star Trek: Voyager, season 3 episode 26 (season finale) "Scorpion: part 1" and season 4 episode 1 (season premier) "Scorpion: part 2", season 4 episode 16 "Prey", season 5 episode 04 "In the Flesh"
Template:Spoiler Species 8472 were discovered by the Borg in 2373 when they invaded fluidic space. The Borg quickly discovered that 8472 was immune to assimilation, and that their technology was no match for them. They are one of the only species so advanced that their ships were able to destroy Borg cubes in seconds. Species 8472 then invaded the Delta Quadrant in retaliation to Borg aggression, and began a systematic ethnic cleansing of the Borg and other innocent species. Over 4 billion drones were lost, as well as at least 9 planets. When Voyager realized that it had no choice but to go through Borg space in order to continue home in any kind of timely manner, Captain Janeway hatched a plan to create a weapon to kill Species 8472 and use it as bargaining chip with the Borg in exchange for safe passage through Borg space. The Borg accepted. In conjunction with Janeway, the Borg developed a high-yield warhead armed with modified nanoprobes, developed by the Emergency Medical Hologram, that was extremely effective at killing 8472 and forced them to retreat to fluidic space.
A member of Species 8472 was left in the Delta Quadrant during the retreat and was relentlessly hunted by a group of Hirogen for several months.
Concerned about the threat posed by humanity, Species 8472 built 13 "terraspheres" in the Delta Quadrant and recreated Starfleet Academy within as a staging ground for potential infiltration. The plan was uncovered and stopped by the crew of Voyager who convinced 8472 that the Federation had no quarrel with them.