User blog comment:ImperiexSeed/The oldest being, archangel or leviathan?/@comment-24834479-20150615003312

"Her power appeared to work exactly like the white light of Angels."

It looks the same as the white light that angels use, but there is nothing implying that it has the same impact. There really isn't any reason to believe that her white light has the ability to kill demons, as we have only seen her use it on humans.

Yes. While it's possible that his snoring could effect angels as well, I think that it is much more likely he was talking about using his angel blade.

I'm not saying that the darkness is powering Cain to its own full extent, but we know what the source of the marks power is. The way that Cain easily beat Castiel, I would say that he is easily on the same level as a Seraph. He didn't know the full extent of his potential power, since he believed an archangel was his power source. Should he had known a far greater entity had been empowering him, I believe that he could have channeled more power from the mark.