The Kobali are a sapient humanoid species native to the region of the Milky Way that is known to the Federation as the Delta Quadrant. They are notable for their unusual way of artificial reproduction, which consists of gathering the corpses of other species, which are then simultaneously reanimated and genetically converted into Kobali.
To transform other beings into members of their own species, the Kobali employ a genetic pathogen which converts the host's DNA into Kobali proteins (this might mean the Kobali genetic structure is proteic in nature). Presumably, they only use it on dead individuals in order to avoid conflicts with other species, as assimilating live individuals would be widely perceived as a hostile action.
The converts are then adopted in a Kobali family and affectionately raised as one of their own. Although they are still psychologically the same individuals as they were before dying, the changes in anatomy and physiology cause the converts to start perceiving themselves as Kobali (thinking in Kobali language, developing a taste for Kobali food, etc.). Exactly how much they can remember about their previous life is something that varies from individual to individual. Anatomical features of the Kobali include something called a "multi-spherical brain" with six lobes, and a binary cardiovascular system.