What is The Great Prophecy

The Great Prophecy is a prophecy given by Rachel Dare, Camp Half Blood's oracle. It talks about a great event in which seven demigods will have to save the world. It seems to suggest that the Greek demigods and the Roman demigods will have to work together. The Great Prophecy is: "Seven half-bloods shall answer the call/To storm or fire the world must fall/An oath to keep with a final breath/And foes bear arms to the Doors of Death." (Chapter 10, Piper, p. 120-1).