Some of the first explorers that set out from Sol in early 2600AD found a rich system to the galactic south, called Tau Cygni. They discovered a previously unknown biological compound there that became the base for cloning. It quickly became an important hub for science and biotech, and its influence within the Empire became significant. After the Stormguard sacked the Matrix Vault, Jovian neuroscientists unearthed methods for copying and transferring consciousness. Combining the two discoveries into true cloning became the focus for the Emperor.
When the Emperor sent Stormguard to oversee the operation, they discovered a separatist plot to secede from the Empire. The discovery ignited a Civil War between the Cygan Separatists and the Imperial forces, both of whom wanted to control the scientific discovery. The Separatists were no match for the Imperial Stormguard and lost ground in every engagement. It became quickly apparent that the Separatists were no match for the Imperials.
In a last-ditch effort to defeat the Imperials, the desperate Separatists unleashed bio-engineered creatures, called the Genus, made from the strange cloning compound. The Genus were the stuff of nightmares, strange fleshy, sinewy monsters and driven by an unending hunger and need to consume. The scientists who created the abominations thought they would be hailed as heroes, the saviours of the Separatists. But when the Genus were unleashed, the scientists realized the killer instinct they had built into the was overpowering.
The Genus succeeded in ending the Cygnan Civil war within weeks by annihilating all other life in the Tau Cygni system. They exterminated all other lifeforms and transformed them into new and atrocious creatures and structures. They were unstoppable, procreating by disassembling other lifeforms, injecting the biomass with Genus DNA, and reassembling it into new horrors.
The Genus Brood was driven by twisted instincts to obliterate all other life in the galaxy and they began their insatiable quest by spreading uncontrollably into nearby star systems, wiping out everything they came into contact with and growing stronger with each victory. When it seemed they would never be stopped, the Kolari intervened. Through methods known only to them and the Genus, they shared the reason with the Genus, gifting them the ability to control their killer instinct. They learned that at times greater benefit can be had from peace if only to prepare for an onslaught.
The Genus retreated, filling their home system and conquered worlds with fleshy structures that reformed the creatures as needed, and waited until they were stronger and the time was right.