User blog comment:ImperiexSeed/The oldest being, archangel or leviathan?/@comment-2240918-20111011231531

I think the Leviathans are older, and therefore more powerful. Seeing as Castiel died in Hello Cruel World, in my opinion, this heavily suggests that the Leviathans have been around much longer than both angels and archangels since God created them prior to both angels (if he created them) and mankind.