"There shall not be found among you... one who inquires of Ov"—Deuteronomy 18:10-11.
The Torah forbids us from consulting with an Ov practitioner, to ask him for advice or information based on his Ov experience.
The Ov practice consisted of burning a certain incense and doing certain acts known to the Ov followers. At that point, it would seem to the person engaging in these acts that he hears a voice emanating from beneath his armpit, which would answer questions that he posed.