All of the five flying islands of Skytopia cast shadows, and most of them are vast enough to plunge any unfortunate Earth-dweller caught in them into a second midnight. Hiyokuna, though, is by far the largest island, and hence it is this island Earth-dwellers talk about when they refer to the Shadow.
The Shadow is an enormous stretch of dark, withered forest where the sun never shines. In the morning, its eastern edge is illuminated for a few hours, and in the evening its western edge, but the center of the Shadow never gets brighter than a murky twilight. Strange, evil things live here, creatures of the night that emerge to prey on humans. The Earth-dwellers have tales of the Nightworms, giant black centipede-like monsters, and of owlbears and blackgaunts and other fearsome things.
Most feared and despised, though, are the stunted shadow-men or goblins. It’s said that these twisted creatures were once humans, who were caught in Skytopia’s shadow and turned into monsters. Now, they’re short, thin wretches armed with scraps of night-iron, who see perfectly in the dark and gleefully destroy any human settlement they come upon.