What does Perseus need from the Grey Woman?

Perseus needs the Grey Woman, also known as the Graeae, to provide him with information about the location of the Gorgon Medusa. The Grey Woman possess knowledge of where to find the nymphs who guard the items Perseus requires: a reflective shield, winged sandals, and a cap of invisibility. By obtaining this information, Perseus can successfully prepare for his quest to slay Medusa.