A Great Hawk is a creature living in the Frontier. It seems to be the same creature from before the nuclear destruction and the species survived the war living 10,000 years later and thriving. They seem to be commonly used by trainers and can be further enhanced fitted with armor, video equipment for surveillance, and many other varying technology.
Pikk uses them selling them as one of his hottest items to be used for reckon, weapons, and many other uses.
D strikes a deal with Pikk for his services to use to spy on the Xeno Clan.
They seem to also be sold at a shop in Ligatem known as the "Bird Man".