The Rraey are a species described in Old Man's War as being considerably less advanced than the CDF. They consider humans as a part of a "balanced breakfast" and are even known to have celebrity chefs showing how to best butcher a human. They became a serious problem for the CDF after acquiring technology from the Consu to predict the trajectory of a vessel's skip drives, a feat that was previously considered impossible.

The Rraeys are an alien species that resembles more of a bird than a human. The Rraey are physically described in The Ghost Brigades as being roughly the same size and shape as humans and bilaterally symmetrical, although their knees bend the opposite way. Their eyes and ears wrap all the way around their head implying that they have 360 degree vision. They developed a craving for humans, going as far as creating many dishes for different parts of the body. They are a few decades behind the CDF in terms of technology and weaponry, but nonetheless, still considered a threat to the CDF.

The skip drive detection device given to them by the Consu enabled them to wipe out an entire fleet of CDF ships without any casualties to their own.