The Hork'Bajir were created sometime around 10,000 B.C by the Arn to serve as "tree herders" for the reconstructed and delecate eco system of the planet. Although they appear to be killing machines, the blades are for stripping off tree bark which they eat, and most Hork-Bajir had no concept of violence before the Yeerk invasion. They are among the physicly adept species of the MW, but they only possess the mental capacity of a Human toddler, with the exception of 1 in every 10,000 Hork-Bajir being as smart as a Human. Those Hork-Bajir are called "Seers". The Yeerks saw them as perfect shock troops for their campaign of galactic conquest. They were once peaceful, but when the Yeerks took over them, they were shock troops to the Yeerks. Few are left free today.