Yosoper is the classificatory brother and dark counterpart of the creator Yatoʼ Yos. Where the elder brother fashioned humans, useful plants, game animals and everything good, Yosoper, envious and attempting to emulate him, brought forth instead the harmful, dangerous and evil things of the world. The paired brothers embody the Yanesha understanding that good and ill spring from a single creative act imperfectly doubled, and Yosoper stands as the ultimate source of the malignant beings that afflict the living.