User blog comment:ImperiexSeed/ARCHANGEL or LEVIATHAN!/@comment-5.203.113.73-20130515111500/@comment-3481504-20130515164321

You're absolutely right, they were simply eating away at his vessel, and therefore, him.

Maybe, but Seraphs, such as Castiel, couldn't overpower Leviathans like Dick, Edgar or Joyce.