Since time immemorial the Vel-Teh have been a race of wandering explorers, with an insatiable curiosity, and driven by an inquisitive mind. However, long ago a small off shoot developed that decided to follow a different path. Instead they chose to isolate themselves away to brood and contemplate over the nature of themselves and their unique symbiotic relationship.
Over time reflection led to impatience. Left to dwell in thought and study on their symbiont the small group of Vel-Teh grew arrogant and callous. They set themselves to the task of bending their symbionts to their will, forcing them to accelerate their transformations. The faster they changed, the more aggressive they became, and the more strained the techno-organic symbiont.
No longer in balance, their bodies became rapidly decaying compositions of pale unhealthy flesh and crude roughly formed cybernetics. Seeing only weakness in flesh, these errant Vel-Teh gave themselves completely over, becoming heretics now known as the Kor-Teh. Forever distancing themselves from all former ties to the race from which they came.
In solitude the Kor-Teh became gripped with violence and hatred. Discovering their enhanced rate of cybernetic adaptations were unstable, only one possible solution existed to the Kor-Teh. They would seek out their wayward former relations, and take from them all they had amassed. Once dominant, they would have all the technology and knowledge they could ever need to keep their bodies in full repair. Not to mention erasing those who had wasted their birthright.