Little is known about the bestial human forms who occasionally raid the small outlying farms, and villages of the kingdoms of men. They are Chaos itself given flesh. They are the Children of Chaos, born when the polar gateways of the Old Slann collapsed (-4500 IC), thus heralding the first dominion of Chaos. The fabric of the Realm of Chaos burst into the material universe, warping many of the natural creatures who lived, until now, peacefully on the Warhammer world. From this terrible catastrophic event many mutated creatures were born: the rat-men known now as skaven, the half-men and half-horse centaurs, and the Beastmen who were the most common of this new bestial race. They are called the Children of Chaos because they alone of all Chaos' worshippers understand Chaos and its many perplexing ways and they were brought into existence by its dark energies.

Since the fall of the Old Slann, Beastmen have remained on the verges of humanity. They have grown strong through many millennia of battle and have multiplied to become a very real threat. Even now their numbers can be found in most forests and mountains ranges of the Old World. They are most numerous in the north, the Empire (notably the Drak Wald Forest) and Kislev (notably the Taiga), but even in Tilea and Estalia their presence is felt. Humans there fear that one day they will be overwhelmed by the hordes of Chaos, when in fact the Beastmen have little concern for them and for the most part they pay little attention to humanity. However, should a human wander foolishly into the depths of a forest he would more than likely attract the unwelcome attention of the creatures who live there and should they be Beastmen, the human would never leave the forest alive.