User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-10750309-20130716112029/@comment-6068707-20130716130252

To storm or fire the world must fall.

The prohecy also mentions him in a vauge way. He is the fire, since in Jason's prophecy he was the hammer, and fire is also a symbol of Hephaestus. While the storm is either Jason, son of Jupiter, or Percy son of Poseidon.

He actually was told by Nemesis that the quest would be vital for him, and that he would be the one to help Hazel and Frank. So considering the way the story has led up I believe he is very important. Also isn't he like one of the only two people that can fix the engine of the ship, him and annabeth, so he's kinda important.

P.S. I doubt he will die, if he is the only person that can fix the ship.