User blog comment:Menara/Bianca di Angelo may be one of the 7/@comment-4448732-20111001213653/@comment-3146930-20111001215032

I think he created a portal to the Underworld as the Labyrinth is between the surface and the Underworld, but they went directly down. Also, when he tries to save Percy after Rachel hits Luke with a hair brush, he creates columns of Black Rock, as in Erebus, the black walls of the underwold