User blog comment:Menara/The Mark of Athena Character Art Revealed!/@comment-4430596-20120903194159/@comment-4430596-20120903195525

Given his role in The Titan's Curse, it is pretty safe to assume he is arrogant. And, he technically still a demigod. In fact, the demigod who helped the gods defeat the Gigantes the first time. (In some versions) So, he might think he can defeat the Gigantes again, and now that he is a god, he could do it alone. What I'm saying is his pride could cause him to not open the gates of Olympis.