User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-5850470-20121217235414/@comment-5774152-20121218044247

I think Doors of Death refer to two sets of doors right next to each other or close by each other. That's why monsters from tartaus would be able to escape into the mortal world. Well if the doors are right next to each other then someone from the mortal side could go into tartaus too. So maybe someone from the mortal side could go into tartaus and make the sacrafice instead of Percy and Annabeth. I really don't know what to think about who's going to stay in tartaus if anyone at all. There's many possibiliteis, many theories. But I think it's going to be either Percy or Frank.