The pronouncements of the Delphic oracle were delivered by a priestess, appearing to rise (by a cunning mechanical contrivance) amid clouds of incense on her serpent-throne, from a chasm which cleft to the centre of the earth, in a theatrical display calculated to outscore the appeal of the rival oracle of Zeus at Dodona. Her voice was one of the most powerful influences on the history of ancient Greece. . . .Yet despite the impressive display, the shrine declined in prestige as it became apparent that the messages of the god were politically calculated or purchased by corruption.

Felipe Fernández-Armesto, Truth: A History and a Guide for the Perplexed