Harry Potter- The New Prophecy

No spell can reawaken the dead. Albus Dumbledore himself said so. So how is it possible that witches and wizards who are supposed to be dead are showing up very much alive? And what happens when a new prophecy is discovered? One that talks about the Dark Lords return? Will the wizarding world have another battle on their hands?

Disclaimer: I do NOT own Harry Potter. The books, movies and characters belong to JK Rowling.