User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-5247339-20130622090134/@comment-3146930-20130623002344

In order to make her rise, some sacrifice needs to be made at the top of Mount Olympus on August 1st; one boy and one girl. I think it has to be members of the seven, as Gaea could easily kidnap any two demigods. Not much else is mentioned besides that. As far as stopping her, I guess you could prevent the sacrifice. The House of Hades synopsis also mentions they can prevent it by closing the Doors of Death, but I don't understand why that would stop it.