User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-1515612-20130221033240/@comment-3146930-20130224182408

I know there probably isn't a third camp, but in The Son of Neptune Frank explains how the gods changed from Greek to Roman and how Octavian still thinks there are Greek demigods out there. Then he mentions hearing stories about demigods at Camp Jupiter who left camp to train in the Greek style of fighting and see the gods as Greek. I'm sure that the gods would prevent those that left from finding Camp Half-Blood, so the only logical explanation is that those demigods either died or formed their own camp. In a way, a demigod from this Third Camp could balance the seven, as we would have three Greek, three Roman, and one Roman that acts Greek. It just seems like this huge bit of foreshadowing on Rick's part, but so far it hasn't actually gone anywhere.