Persephone is a who, not a what... -_-
Short summary: She's a godess from Greek mythology. The daughter of Demeter, who got abducted by Hades, the ruler of the Underworld and Persephone later became the queen of the Underworld. She spends half a year there and half a year on Earth.
Most likely "Persephone's close" is a metaphore for "spring is close".