User blog comment:SayuriDarling/The Mark of Athena Official Discussion/@comment-4388405-20121006181920/@comment-4515675-20121006200733

Actually Jason has been possessed ever since TLH. And I quote from the book:

"He gasped, and his eyes flew open. For a moment they were full of light—glowing pure gold."

I'm officially freaked out. Jason had that thing inside of him for six months now. I wonder if it ever took control of him before his fight with Percy.