Those who answer a nighthorse's "call" become riders. Over a short period of time a relationship is formed that is mutually beneficial to both nighthorse and rider: the rider has transport and protection in the Wild (a nighthorse will protect its rider to the death), and the nighthorse receives the comforts of the rider camps in the villages, food, the rich emotional human sendings it craves, and "memory". On its own, a nighthorse does not have a good memory, but with a rider the ambient is filled with memories and the nighthorse can remember things!