From Introduction:
Some have said that within the hearts of men, there is a beast that wishes to escape. But the psicanthrope has looked not into his soul, but his subconscious, and has sought out the creatures within and has learned to remake himself in their form. A psicantrhope fulfills a primal urge within himself to become the animals that he has tapped with the animal affinity powers, and learn to master their form in addition to his own.
Most psicanthropes are egoists, masters of Psychometabolism, or psychic warriors. Without fail, all psicanthropes are strong specimens of their kind due to the physical demands of their art. Few seek any formal training in these arts, but find the path unfolds before them as they seek the forms of animals. Most seek out a life away from civilization, often among the animals that the psicanthrope feels most at home with. In these environments, it is not surprising that most psicanthropes are initially mistaken as druids or natural lycanthropes. Some powerful psicanthropes (level 8 and above) can spend their entire day in animal form, only returning to human shape when the need for tool-use becomes apparent.