User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-10218971-20130808090805/@comment-3146930-20130808161505

Rick Riordan has been known to stretch the true sometimes. Maybe he was so evil in life that he became a monster. Another option is that he found a way out of the Underworld, as the Doors of Death are just the fastest way out of the Underworld, but they said in The Demigod Files that new exits and entrances are appearing all the time.