Arcto Kandlios the first Swarm King corrupted his former Arc'Belaren comrades to serve in his Swarm, these were the first Couriers used to lead the numerous short-lived Kandlia warriors. after Kandlios took over and renamed planet Darthur the Swarm began corrupting random organisms and sentient organisms to build up their forces.
After the disaster at Myst, Sentien, knew his followers were growing tired of his rule, he sent his son Spline to instigate a rebellion within the ranks of the couriers, however it wouldn't be until a few years later that this rebellion would actually begin.The conflict began on Sholalusz after Harkoff tricked the Couriers into powering him up, the conflict had many small skirmishes across the stars, until the attack on Earth, and the subsequent defeat on Frontier , where the conflict still lies unresolved.
Former Courier Draliska had grown incredibly intelligent in his eleven years of life, he realized the incompetence of the Couriers and instead created a force of commanders known as the Imperial Directors, no longer being required to serve on the frontlines, the Directors could control their swarms from worlds away as if they are right in front of them, the directors would not have to be put in harms way at all, this did not go well for the remaining dozen couriers that lived, they rebelled, just as Draliska had predicted.
After a lengthy free for all, Draliska was proven correct as his directors had destroyed the couriers and their wayward swarms, once word of this spread to Terran-Natogytt Space, Draliska's enemies were filled with fear. Draliska had finally accomplished his goal, a new empire, the Draliksan Empire.
The last few dozen Couriers including Cruor and Harkoff had eluded Draliska's wrath up until after the UTSEA Victory against the Dark Ty'Ger, shortly after, Draliska offered the couriers a choice, surrender and be genetically modified into imperial directors, or die. the Couriers surrenderd having been depleted by the Dark Ty'Ger invasion.
The Couriers are now completely extinct.