User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-4430596-20130120031913

It's time for Frodo's prophecy rundown!

Seven Half-Bloods will answer the call If you haven't figured this one out yet... well, its been the plot of the last three books.

To storm or fire the world must fall This one is trickier. Storm or fire could be a reference to demigods: Percy/Jason (maybe Percy and Jason) is storm. Leo is fire. It could be a reference to their parents. It could also be something completely different no one has thought of. World could be Gaea, the literal world. It could also being saying the world is going to end, as in Gaea come back and its December 21st all over again. Or, as with storm or fire, it could be something completely different.

An oath to keep with a final breath I don't have the slightest idea. Maybe something to do with Piper (hopefully) or Jason's last breath as she keeps thinking about it?

And foes bear arms to the doors of death. Most likely refers to Greek and Roman demigods(foes) going to the Doors of Death with weapons. It could be slightly different, but probably not.