From publisher blurb:
The centaurs make no claim on the Endless Steppe. Rather, they see themselves as its protectors chosen by the spirits of the plains to preserve the lands against the invader, to keep their lands pure, sacred, and free from the rapacious humans who would transform it to suit their needs. Thus the centaurs roam the Steppe, watchful for interlopers from beyond the mountains so they can drive them back as they have so many times before.
This installment in the Poisoned Pages series makes it possible to play centaurs in Shadow of the Demon Lord. A more powerful ancestry than those presented in the main rulebook, centaurs use special rules to make them compatible with other characters in the group