User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-3146930-20121222220541

Dark's Crazy Theory Time

So I at this very second had an idea, a crazy idea. So the Doors of Death need to be closed from both sides. Everyone thinks that Percy or/and Annabeth need to stay behind in order to close the doors on the Tartarus side. However, there are other things in Tartarus besides Percy and Annabeth. There are monsters, Titans, and considering all the undead rising, the souls of people.

What if Leo, Piper, Jason, Hazel, and Frank manage to get the two sides to stop fighting on the Mortal side of the doors and fight together to defeat the forces at the House of Hades. Meanwhile, Percy and Annabeth manage to convince the beings in Tartarus to fight against Gaea and the Gigantes, as Gaea was the one that asked Zeus to defeat Kronos, making her partly responsible for any Titan in Tartarus. Foes bear arms to the Doors of Death, Titans/monsters and demigods working together, two foes working against a common foe.

Now you may be thinking to yourself: "Dark, there is no way that could happen."

And you're right, but it is an idea.