Species 8472

"The weak will perish!"

- battle-cry of Species 8472

"Species 8472" was the Borg designation for an alien race otherwise known as the Undine, inhabiting a dimension known as "fluidic space". The USS Voyager (NCC-74656) came into contact with this species in the 2370s, during a conflict between them and the Borg in the Delta Quadrant. Of all the races known to Starfleet during the Borg's campaigns to assimilate other sentients, Species 8472 proved to be one of the toughest, successfully resisting assimilation and inflicting major damage to Borg ships and resources. 

Star Trek: Constance
Species 8472, referred to as the Undine had infiltrated the Alpha and Beta Quadrants at some point prior to 2409. Then Cadet Drash Kada had intercepted Klingon transmissions that alluded to the Undine infiltration of the Gorn Hegemony, which was filed as unimportant by the leaders of the Federation. An Orion KDF officer would go on to execute an Undine infiltrator on the planet Fenra IV in an attempt to convince the Fenarans to join the Klingon Empire.

The exact reason behind the infiltration was unknown, as the Federation has made no incursions into Fluidic Space.

Star Trek Online: Valkyries
Similarly, the Undine (Species 8472) infiltrated the Alpha and Beta Quadrants prior to 2405. In that year, an Undine infiltrator murdered the crew of a Ferengi freighter and attempted to infiltrate the USS Nautilus (NCC-31910) by murdering and replacing Lieutenant Emma Frost. The attempt was foiled when a private investigation by Ensign Carlin Agran exposed the infiltrator, which was subsequently killed by Commander Antori Drel, Captain, and a security team. Section 31 expressed interest in how the infiltrator was able to change its form so readily, but the body was destroyed. At this time Franklin Drake claimed that Section 31 had several captured infiltrators in custody, including. The reason for this attempted infiltration was unknown and Starfleet Security covered it up ("The Best Revenge").


 * The Bait and Switch shared universe closely follows, but with some differences.

In 2410 the Undine launched a massive assault on the capitals of the Klingon Empire and Federation, which was repulsed at great cost but led to the end of the. The Undine continued to battle the resulting Federation-Klingon-Romulan alliance for some time, including sending a planet killer to unsuccessfully attack Cardassia Prime. USS Valentine was lost in that battle. (Reality Is Fluid, The Wrong Reflection)

Not long after the First Battle of Qo'noS, USS Bajor was accidentally transported to fluidic space by the Bajoran wormhole and encountered a large force of Undine vessels which did not attack. A Saurian crew member, Ensign Arak Esplin, discovered that these ships had different markings from the ones attacking the alliance when viewed under ultraviolet light. Captain Kanril Eleya was able to open a dialogue and discovered that these Undine were of another tribe or clan from the one conducting the war in normal space. She was able to convince them to allow Bajor to leave unharmed and direct their wrath on the enemy tribe and the Iconians duping them. (Reality Is Fluid)

Later that year, at Kanril's suggestion, Rear Admiral Tuvok was able to convince the Undine to come to the aid of the Federation forces defending from an Iconian invasion. The Undine slaughtered the inbound Herald armada with only light casualties. (Beat the Drums of War)

The Undine joined with a multinational fleet in Operation Mockingbird, breaching the Herald Sphere with their weapons so a sunkiller weapon could be fired into its sun, ending the Iconian invasion. ("Light on the Horizon")