The Borg co-opt the technology and knowledge of other alien species to the Collective through the process of "assimilation": forcibly transforming individual beings into "drones" by injecting nanoprobes into their bodies and surgically augmenting them with cybernetic components.

The Borg represented a new antagonist and regular enemy which had been lacking during the first season of Star Trek: The Next Generation (TNG); the Klingons were allies and the Romulans mostly absent.

The Borg, however, with their frightening appearance, their immense power, and their sinister motive, became the signature villains for the TNG and Voyager eras of Star Trek.

TNG writers began to develop the idea of the Borg as early as the Season 1 episode "Conspiracy", which introduced a coercive, symbiotic life form that took over key Federation personnel.

[4] Individual Borg are referred to as drones and move in a robotic, purposeful style, ignoring most of their environment, including beings they do not consider an immediate threat.

The nanoprobes rewrite the cellular DNA, altering the victim's biochemistry, and eventually form larger, more complicated structures and networks within the body, like electrical pathways, processing and data-storage nodes, and ultimately prosthetic devices that spring forth from the skin.

In the Star Trek: Voyager episode "Mortal Coil", Seven of Nine told Neelix the Kazon were "unworthy" of assimilation and would serve only to detract from the Borg's quest for perceived perfection.

A Cube was first seen during the Borg's introduction in the Next Generation episode "Q Who", which established the vessel as vastly exceeding the capability of Enterprise – the main ship of the series and Federation flagship – to defend against or escape it without outside intervention.

The episode "The Best of Both Worlds" and the film Star Trek: First Contact both depict single Cubes as critical, military threats; capable of fighting or defeating an entire fleet of ships.

Assimilation by tubules is depicted on-screen as being a fast-acting process, with the victim's skin pigmentation turning gray and mottled with visible dark tracks forming within moments of contact.

In Star Trek: First Contact an assimilated crew member is shown to have a forearm and an eye physically removed and replaced with cybernetic implants.

The introduction of the Queen radically changed the canonical understanding of the Borg function, with the authors of The Computers of Star Trek noting: "It was a lot easier for viewers to focus on a villain rather than a hive-mind that made decisions based on the input of all its members.

In the series finale, the Queen reveals that the Borg were decimated following the events of Star Trek: Voyager and she now seeks to evolve and propagate her race while annihilating all other life forms in the galaxy, having cannibalized many of her remaining drones to survive.

[15] They decide to return him without the virus, but in the sixth-season episode "Descent", a group of rogue Borg who had "assimilated" individuality through Hugh fall under the control of the android Lore, the "older brother" of Data.

First Contact introduces the Borg Queen as played by Alice Krige, who later reprised the role on United Paramount Network for the finale of Star Trek: Voyager.

[14] The episode's prologue depicts Benjamin Sisko (Avery Brooks) as First Officer on the USS Saratoga, in the Starfleet armada dispatched to confront the Borg at Wolf 359.

Throughout the remainder of the series, references to the Borg are occasionally made, including the intent behind the design of their ship, USS Defiant, and the battle from Star Trek: First Contact being used as a plot point in the fifth season; when Starfleet is spread too thin to deal with a Dominion incursion.

Juliette Harrisson, writing for Den of Geek in 2017, gave actress Susanna Thompson and Alice Krige as Borg Queens an honorable mention in a ranking of best guest-stars on Star Trek: Voyager.

[20] In the sixth-season episode "Collective", the crew of Voyager encounter a damaged cube that is holding Tom Paris, Neelix, Harry Kim, and Chakotay hostage.

In "Shattered", a freak accident allows Chakotay to travel to various time-periods in the ship's history; including the events depicted in "Scorpion", where he interacts with the fully assimilated drone Seven.

[22] In the second season, a damaged Borg Queen is recruited by Picard to help him and his crew travel into the past and prevent the creation of the xenophobic and totalitarian "Confederation of Earth".

Driven insane by loneliness and forced to resort to cannibalism of her own drones to survive, the Borg Queen no longer seeks assimilation; but rather evolution, propagation, and the annihilation of all other lifeforms in the galaxy.

In the later episode of Star Trek: Voyager, "Dragon's Teeth", Gedrin, of the race the Vaadwaur, says that before he and his people were put into suspended animation 892 years earlier (1482 A.D.), the Borg had assimilated only a few colonies in the Delta Quadrant and were considered essentially a minor nuisance.

In the novel Lost Souls (the third book in the Star Trek: Destiny trilogy), the Borg are revealed to be the survivors of the Caeliar city Mantilis.

Thrown across the galaxy in the Delta Quadrant and back in time to about 4500 BC by the destruction of Erigol at the climax of Gods of Night, the first book in the trilogy, a group of human survivors from the starship Columbia (NX-02) and Caeliar scientists try to survive in a harsh arctic climate.

The gestalt group mind is perverted to become the collective, driven by Sedin's desperate hunger and need to add the strength, technology, and life-force of others to her own.

It was not until the end of the TOS era that she made contact with the main Borg force and became a queen before she was finally killed in a fleet of Starfleet, Romulan, and Klingon ships led by Picard.

David revisited this concept in a 2007 sequel novel, Before Dishonor, which features the Enterprise-E working with Spock and Seven of Nine to reactivate the original planet killer to stop the Borg.

In the story, titled "The Worst of Both Worlds", Jean-Luc and his crew are trapped in an alternate dimension where the Borg have destroyed the Federation and assimilated Earth.

The crew encounters a more battle-hardened version of themselves, the last survivors of the Federation led by now Captain Riker, struggling to survive and continue the resistance.