User blog comment:ImperiexSeed/The oldest being, archangel or leviathan?/@comment-5110811-20150606210717/@comment-3045936-20150611015141

I always thought this. Leviathans can sense supernatural creatures if they possess a physical body. Crowley is in a human so were the two angels that Edgar killed. Bobby didn't as a ghost. I think the reason magic can harm them, is cause magic is universal. We also know the soul is magical in nature, so it adds theory to why 30-40 million powered Castiel to the point of having all Leviathans, inside and not break down instantly.

And now we know that some witches naturally have magical abilities without making deals with demons. I always thought since Eve is somewhat connected to the Leviathans, and as she said know what makes Angels tick. So maybe the Leviathan have like similar ability or function that cuts of an angel from its grace when near one. So my point, it doesn't matter how strong one is. If your cut of from that power, it's the same as not having it.