In the 'Goblet of Fire' when Harry has relating what happened after he touched the Triwizard Cup and faced Voldemort, he talks about 'Priori Incantatem'-the reverse spell effect. He mentions that an echo of Cedric came out of Voldemort's wand. At this point, Sirius says, "Diggoru came back to life?" And Dumbledore says, "No spell can awaken the dead."
Am I the only person who thinks that this could turn out to be a very important piece of information in one of the coming books? Perhaps even in the final duel between Harry and Voldemort?