What is "lethaea"

Lethaea is a mythological character briefly mentioned in Ovid's Metamorphoses. Due to her vanity, she was turned to stone at Ida by the gods. Her lover Olenus wished to share in the blame, and so shared her fate. The story is used as a metaphor for how stunned Orpheus was after a failed attempt to bring back his wife from the underworld. It was as if he too were turned to stone.