User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-10867502-20130616004340

This theory just hit me like a ton of bricks, in the secret files book (blue) there was the sword of hades story. to sum it up hades created a sword that contained the mystical keys of death. in the book it mentioned it was double bladed. then in the  last olympian when hades comes to save the day it says on page 317 " and he drew a double bladed sword". then when he charges the barrier khronos made around the empire state building he drops the sword and begins fighting with his staff. the sword and keys disappear. now they are having problems with the doors of death bieng unlocked...