Posleen

Posleen are a fictional alien race, created by the Sci-Fi author John Ringo for his Legacy of the Aldenata series of books. The Posleen are a race of genetically engineered reptilian centaurs, supposedly designed by the long lost race - the Aldenata - to be the ultimate warriors. The Posleen invasion is shaped by their (over)engineered physiology - Posleen are omnivores and capable of sustaining themselves by eating a wide variety of organisms(including humans) as they must eat almost constantly or starve. Inevitably, they exhaust the resources of every environment they inhabit, resulting in a phenomenon they call orna'adar - planetwide conflicts that always end in nuclear holocaust, with the survivors fleeing in starships to repeat the process on new worlds leaving lifeless radioactive desert planets in their wake.