The Borg Queen's vessel was an octahedron-shaped starship that was used by the Borg Collective. In Federation encounters with this starship design, it was utilized by the Borg to transport the Borg Queen. The ship was heavily armed, well protected, and, like all Borg ships, capable of transwarp speeds.
The vessel was present when Species 10026 was assimilated in 2375; Seven of Nine and the Borg Queen were aboard while this assimilation took place. Later, the vessel pursued the Delta Flyer when it escaped from the Unicomplex after rescuing Seven. The vessel was destroyed when the USS Voyager collapsed a transwarp conduit it was traveling in. (VOY: "Dark Frontier")
No designation was formally given for this starship design. It remains unknown whether any other ships of this type exist.
The script of "Dark Frontier" described this vessel merely as "massive" and "a complex, distinctive geometric shape we've never seen before."
Because senior illustrator Rick Sternbach – who usually designed the ships in Star Trek: Voyager – was busy with other aspects of the production for the double-length episode "Dark Frontier", the challenge of designing the Borg Queen's vessel fell to Dan Curry. To do so, he worked closely with Brandon MacDougall who designed and made the 3D model at effects house Foundation Imaging. (Star Trek: The Official Starships Collection, issue 109, p. 10)
The Borg Queen's vessel followed the design ethos of previously established Borg craft while also being deliberately unique-looking. "For the Borg Queen's ship, we decided to make it distinctive and instantly recognizable as different [than] the rest of the Borg fleet," explained Curry. "Obviously, Borg aesthetics dictated that it should be some sort of geometric form [....] It was just a matter of coming up with an appropriate geometric form, and I think the diamond shape was a group effort." (Star Trek: The Official Starships Collection, issue 109, pp. 10-11; Star Trek Voyager: A Celebration, p. 206)
Curry and MacDougall also wanted to add a sense of liveliness to the craft. This notion was inspired by the opportunity to feature moving starship parts in VOY, which had only recently become doable thanks to the series having changed to depicting ships with CGI rather than with practical studio models. To fulfill their goal of making the Borg Queen's ship look dynamic, Curry and MacDougall decided the outer structure could spin around the center when the ship was in motion. (Star Trek: The Official Starships Collection, issue 109, p. 11)
Once the basic form of the vessel was settled on, MacDougall was given the task of filling in the finer details, including the placement of shipboard weapon systems. "The lack of need for cannon-like structures and the complex details of the ship allowed great flexibility," explained Curry, "and we could make weapons emanate from wherever we wanted." (Star Trek: The Official Starships Collection, issue 109, p. 11)
Ultimately, Curry was highly pleased with MacDougall's work on the design, remarking, "Brandon's final version was brilliant." (Star Trek: The Official Starships Collection, issue 109, p. 11)
Foundation supervisor Robert Bonchune thought the aim of making the craft appear distinct was successful. He commented about the vessel, "That's totally different [....] It's not like any Borg ship we have ever seen." (Cinefantastique, Vol. 31, No. 11, p. 33)
According to the video game Star Trek Armada (and many other games), this ship class is referred to as a "Borg diamond", due to its shape and the fact that it follows the naming conventions used in describing the cube and sphere (though if the naming convention is properly adhered to, "Borg octahedron" is the more applicable designation).
In Star Trek Online, the Borg Queen commands a vessel of this class, termed the "Borg Queen's Octahedron", during an assault by Battle Group Omega against the new Unicomplex being built in the Beta Quadrant ("Hive Onslaught"). Another vessel of this class also appears during the multiplayer event "Borg Disconnected", where it engages in a four-way battle between an Undine Dreadnought, a Voth Citadel Dreadnought, and a fleet of Delta Alliance (Federation, Klingon, and Romulan Republic) ships during three simultaneous attacks on the Delta Quadrant's Unicomplex.