Supay is the lord of Ukhu Pacha, the Andean world below, and of the dead. To understand him it is essential to separate the pre-conquest Andean figure from what Spanish Christianity made of him, for the two are quite different. In the pre-conquest Andean understanding, Supay was ambivalent rather than evil: the inner world over which he ruled, Ukhu Pacha, is the realm of the dead and the ancestors, but it is also the source of fertility, the place from which the crops grow up and where the metals and minerals of the earth are generated, so that the lord of that world was a power to be propitiated and kept in good relations with, not simply opposed. Like much in Andean religion, he embodied the recognition that the powers of the earth and the underworld are dangerous and must be respected and given their due, but are also the source of essential goods. With the Spanish conquest and evangelisation, this ambivalent lord of the inner world was reinterpreted through Christian categories: the missionaries, seeking a word for the Devil of Christian teaching, took up the name Supay and applied it to the diabolical, so that in colonial and later usage Supay came to be identified with the Christian devil, a wholly evil figure. Yet the older Andean sense was not simply erased.
In the mining regions of the Andes, the being sometimes called El Tio, the "uncle" who rules the inside of the mountain and the mine, to whom miners make offerings for safety and for good ore, preserves much of the ambivalent, propitiated lord of the underworld beneath the Christian overlay; and Supay figures prominently in Andean festival and dance, most famously in the diablada, the dance of the devils. Andean religious culture is living and has continued to blend indigenous and Christian elements over the centuries, and Supay stands as a clear example of how a colonial reframing recast an ambivalent native power as the Christian devil, while the older understanding persisted beneath and beside it.