<P> Despite their absence for the vast majority of the series beyond the pilot, references to the Borg, as well as the Wolf 359 massacre, are made occasionally throughout the series . In fact, the USS Defiant, a primary starship setting from the third season onwards, is explicitly stated to have been designed as a countermeasure against the Borg though it is later used against the Dominion . In addition, the battle from Star Trek: First Contact is used as a plot point in Season 5 as Starfleet is spread thin to deal with a Dominion incursion . </P> <P> In First Contact, the Defiant is heavily damaged during a battle with the Borg; the ship is later declared' adrift, but salvageable', which allowed Deep Space Nine's producers to retain their signature starship . </P> <P> The Borg make frequent appearances in Star Trek: Voyager, which takes place in the Delta Quadrant, the region of the galaxy from which the Borg are believed to have originated . The Borg are first discovered by Voyager in the third - season episode "Blood Fever". Chakotay discovers the body of what the local humanoids refer to as "the Invaders"; which turns out to be the Borg . In "Scorpion", the Borg are engaged in a war of attrition against Species 8472, whose biological defences, developed as a feature of their evolution in fluidic space, are a match for the Borg's nanoprobes . In one of the few instances of the Borg negotiating, in exchange for safe passage through Borg space, the Voyager crew devises a way to destroy the otherwise invulnerable Species 8472 . A Borg drone, Seven of Nine, is dispatched to Voyager to facilitate this arrangement as Captain Janeway refuses to allow the Borg to use neural implants for communication with the Voyager crew . </P> <P> After successfully driving Species 8472 back into their fluidic space, Seven of Nine attempts to assimilate Voyager but is severed from the hive mind and stripped of most of her Borg implants, becoming a member of Voyager's crew . Seven of Nine's rediscovery of her individuality becomes a recurring theme throughout the series . Flashbacks and allusions in several episodes, such as "The Raven", establish that before her assimilation, Seven of Nine was Annika Hansen, the child of scientists who studied the Borg in the Delta Quadrant independent of the Federation . Unfortunately her parents were assimilated into the collective with her, but her father makes a temporary appearance in the final episode of Voyager . </P>

When do the borg first appear in voyager