The Na'kuhl were an alien race from the 29th century, and a faction in the Temporal Cold War, vehemently opposed to the Temporal Accord. They were led by Vosk, a dangerous fanatic who viewed time travel as his innate right, despite the damage that might be done to the timeline. (ENT: "Storm Front")
At some point in time, a faction of Na'khul contacted elements within the Klingon Empire, seeking to manipulate them (presumably as part of the Temporal Cold War). This eventually led to Admiral B'Vat's discovery of a planet killer device in the T'Ong Nebula. B'Vat tried to use the device to plunge the galaxy into a state of perpetual war, but was defeated by a group of Starfleet and Klingon Defense Force officers. (Star Trek Online)
Sometime in the 29th century, the Na'kuhl fleet fought a large battle against Starfleet and the Vorgon. When the Phoenix-X traveled into this battle, Lieutenant Amp, a computer virus, was used to cripple the Na'kuhl fleet by infecting the ships' computer systems. This infection was able to filter into every ship, then causing permanent damage to the Temporal drives on those Na'kuhl vessels with time-travel ability. By this time, nearly all Na'kuhl time-travel ability was wiped out - except for the ship in which Ghrath was employed. ("Temporal Doom! Part III")
In 2411 the Na'kuhl were a poorly known species of isolationists living in Tzenketh Sector. The Borg Queen acquired her time travel technology from an alternate timeline version of the species. (Bait and Switch: "Brother on Brother, Daughter on Mother")
- The conversation in question states that the events of the Temporal Cold War never took place in Bait and Switch's primary timeline, the timeline where they did take place having been wiped out entirely due to conflicting temporal incursions.