Mass Effect 2 & Mass Effect 3
Although they resemble a mammal-reptile cross, the vorcha have no terrestrial analogue. They are humanoid in form, but vorcha have "clusters" of non-differentiated neoblast cells, like those of Earth's planarian worms. Damaged vorcha cells mature into specialized structures to alleviate injury or stress. Transformations include thicker skin following injury, lung adaptation for barely-breathable atmospheres, and stronger cardio-skeletal muscle under high gravity. Skull capacity and brain size do not change, and vorcha rarely make more than one somatic overhaul.
Vorcha assault each other frequently, causing their young to gain strength, intelligence, and resilience. As a result, vorcha see inflicting and receiving pain as normal communication. Few vorcha study professions, in part because their average life expectancy is only 20 years. Because vorcha can eat and breathe nearly anything, they can live almost anywhere, but racism prevents them from integrating into most societies that dismiss them as vermin. They have few employment options beyond krogan mercenary bands.