The identification of the relief as depicting "Lilith" has become a staple of popular writing on that subject. Raphael Patai (1990) believes the relief to be the only extant depiction of a Sumerian female demon called "lilitu" and thus to define "lilitu's" iconography. Citations regarding this assertion lead back to Henri Frankfort (1936). Frankfort himself based his interpretation of the deity as the demon Lilith on the presence of wings, the birds' feet and the representation of owls. He cites the Babylonian Epic of Gilgamesh as a source that such "creatures are inhabitants of the land of the dead". In that text Enkidu's appearance is partially changed to that of a feathered being, and he is led to the nether world where creatures dwell that are "birdlike, wearing a feather garment". This passage reflects the Sumerians' belief in the nether world, and Frankfort cites evidence that Nergal, the ruler of the underworld, is depicted with bird's feet and wrapped in a feathered gown.