User blog comment:ImperiexSeed/The oldest being, archangel or leviathan?/@comment-3481504-20120611213733

I believe Archangels > Leviathans ONLY, however I will admit.... that Leviathan have something useful Archangels don't have, AND that's memory absorption - from anyone they touch, they gain their memories.

Like, having been in Castiel, the Leviathan know everything Cas does, like what Heaven is, who Lucifer is, and even what Lucifer's Cage looks like.