Humanity, too, has been changed. The changes are widespread, and the causes have been difficult to determine and impossible to reverse. These changes have caused more dread and anxiety among humanity than all the other monsters combined.
Zombies (aka shadows, echoes, hollows, or blanks) are those whose conscious minds seem somehow to have “burnt out.” Zombies will maintain basic instincts, behaviors, and powerful habits, but nothing complex. They are often seen wandering in groups, moving away from danger, towards food and warmth. They do react with some intelligence towards their environment, for example, taking shelter from rain. In green zones, zombies usually survive about four months, or until winter, whichever comes first. What turns people into zombies remains a total mystery, but the phenomenon is global and constant.
Ghouls are habitual cannibals that have fallen prey to a mysterious disease, warping their features, and rendering them obligate carnivores. Their jaws lengthen, forming a short muzzle, their backs hunch, and their eyes become highly sensitive too light, forcing a nocturnal lifestyle. The disease is passed from mother to child, with affected children having all the associated changes at birth. Such children are perfectly healthy, but must suckle on blood to survive until they can handle solid food. The most popular hypothesis is that the changes are caused by prions, much like kuru, but gathering enough samples to test it has proven difficult and dangerous.
Transplants are intelligent, well-educated, and rarely with a previous history of mental illness. Every so often, these sorts of people become possessed with a powerful new drive, pushing them to abandon any previous responsibilities and delve deeply into historical, archeological, or paleontological mysteries. This lasts from five to ten years, at the end of which their old personality returns, with no memory of what had happened or why. Its cause is unknown: it is associated with a distinct pattern of neurological changes, but they seem caused by the illness instead of vice-versa.