What exactly has been chasing the Vasari? Why are they on the run?

The Vasari were conducting experiments on mammalian species discovered on a remote terran planet on the outer ring of the Vasari Empire. Isolated from each other, the captives did not appear to pose a threat with their aimable features and peaceful nature. Together the furry creatures possessed a power greater than the Vasari had ever known.

The small muliticolored creatures each bore a unique symbol on each of their their chests. Under extreme duress the creatures projected a striking beam of light from their chests, combining to form a concentration of energy that penetrated all nearby matter, obliterating the labs, nearby ships and structures. 

The omnipotent group unleashed a path of destruction on the nearby Vasari homewords - their powers growing in number as more of the creatures revealed themselves from hidden domains in the local atmospheres.  The Vasari sounded a empire wide alarm for a complete evacuation. A small portion of the ancient empire could escape the wrath unscathed by the relentless brutality of the species. 

Vasari Nemesis Concept art revealed