The bad guys wear black hats. Observance of the polarity in nature reveals that fact. Each day has a night. The moon has a light and a dark side. The seasons change each year from long, light-filled summer days, to long, dark winter nights.
Night is the time to refuel our energies.
Winter is the time when the Earth retreats into herself to recoup her energies. Animals take advantage of this time to do the same, retreating into dark caves and underground burrows in hibernation. In each of these instances, the dark side is present with a place and time for rest and renewal. The topic of our shadow selves seems to be getting more media attention. The Shadow knows.