The Swarm backgroud

Before becoming the interstellar menace known as the Swarm, an insectile race called Kucharn existed as a series of hives, each with its own collective consciousness. While the colonies competed with one another for resources on their home world, many peacefully worshipped Hylax. Some believe that deity was once a Kucharn who ascended to godhood, though no real evidence of this theory has been discovered.
The Swarm was effectively born when a Kucharn colony developed the ability to consume the intelligence and genetic material of others, creating creatures that were more than the sum of their parts. In a matter of years, this new collective became the planet's dominant species, eventually developing the powers of spaceflight and leaving its world to find others to destroy and devour. Saddened by this development, Hylax abandoned her former children and turned her attention to other sentient species in the galaxy.
As the Swarm spread across the cosmos, it conquered countless other species and left only dead worlds in its wake. It seemed nothing could stop it, as the hive twisted and mutated its own genetic material, adapting to any challenge set before it. Each of these changes created powerful specialized weapons of war, which the Swarm used to continue its campaign of devastation. Driven by its insatiable hunger and instinct to expand, the Swarm has no desire to negotiate terms of peaceful surrender with those it overruns.
During the Gap, a seemingly random mutation with the Kucharn genome created an independent subcolony species whose components could think for themselves: the first Shirren. Thanks to the confusion sowed when that period of forgotten history ended, the Shirren were able to flee from the Swarm across the stars. As they did so, Shirren came to terms with their existence and their love of free will and choice. They were also discovered by Hylax, who welcomed them into her divine embrace and gave them the spiritual tools to survive their exodus.
As the Shirren migrated, they mingled with other sapient species, settled worlds of their own, and built monuments to the Forever Queen, including a monastery on an icy comet and a temple built upon a site that resonated with psychic energy. The Shirren eventually reached the Pact Worlds in 83 ag, entreating the system for safe harbor and warning of the dangers of the Swarm. These words of caution would not be realized until almost 2 centuries later, when the Swarm arrived in a bloody attack on both the Pact Worlds and the Veskarium that was stopped only once the two joined forces in 291 ag.
While the death toll in the war against the Swarm left an indelible mark on the Veskarium and the Pact Worlds, the Swarm was also affected by its only defeat in recorded history. The hive mind learned of the Shirren presence within the Pact Worlds, and though until this point the Swarm held no more regard for its missing "children" than a human would miss a single skin cell, the hive mind began to remember the Kucharn connection to Hylax. A tiny mote of resentment toward the Forever Queen for her abandonment began to fester, and in 318 ag, the Swarm attacked the Chuuva system, where the Shirren had built a colony during their exodus.
Being a peaceful planet, Ilemchuuva was conquered quickly, and with the deaths of thousands of Shirren, the Swarm hive mind caught a glimpse of the Shirren travels immediately after the Gap. The Swarm then formed a subcolony to trace this exodus in the hopes of discovering important sites holy to Hylax and claiming some of her divine power for its own.