Of all the beings that haunt the rain-soaked archipelago of Chiloé, off the southern coast of Chile, none carries a horror quite like the Invunche — because his horror is not what he does. It is what was done to him. The Caleuche takes sailors; the sea-spirits take the drowned; but the Invunche took nothing from anyone. He was taken. Somewhere at the beginning of his legend there is always a human infant — a firstborn son, stolen from his cradle or, in the darkest tellings, sold by his own desperate family — and everything monstrous about him afterward is the workmanship of men.

The archipelago of Chiloé, off the rain-drowned coast of southern Chile, is one of the most densely mythologized landscapes in the Americas — an island world of fog, potato fields, wooden churches, and temperate rainforest so thick that daylight enters it as rumor. Chilote tradition populates this world completely: the ghost ship Caleuche gathers the drowned into its luminous crew , the Pincoya dances the abundance of the shellfish beds , warlocks convene in their cave near Quicaví — and in the forest, squat and terrible, waits the Trauco. He stands, the tradition says, no higher than a man's waist: a gnarled dwarf of the woods, clothed in ragged quilineja fiber, faceless or nearly so, legs ending in stumps without feet, carrying a stone hatchet or a twisted staff called the pahueldún . He is hideous past description. And he is, in the whole inventory of world folklore, perhaps the most notorious seducer — for the Trauco's power lies not in beauty but in breath and gaze, an...