Their supreme adaptability, vicious demeanor, and rapid breeding cycle have made them ubiquitous and dangerous pests on many worlds. Virtually everywhere the krogan have been, varren infestations have followed, wreaking havoc with the native ecology. The krogan have had a love-hate relationship with varren for millennia, alternately fighting them for territory and embracing them as treasured companions. To this day, krogan raise them as beasts of war. A common subgenus of varren has metallic silver scales, leading to the rather unusual nickname "fishdogs".