User blog comment:ImperiexSeed/The oldest being, archangel or leviathan?/@comment-190.92.7.204-20150612220839/@comment-5961531-20150615085617

She also used it on the police station, that she blew up, no different to how an Angel's white light would have done.

Snoring...? Why the sarcasm?

That's obviously not how the Mark works. The keeper of the Mark doesn't need knowledge of the Mark to access it's power, as we've seen plenty of times. The Mark acts on it's own, granting it's power to the wearer with or without them having the knowledge.

Cain defeated a weakened Castiel with a borrowed grace. A grace more than likely from a regular Angel. Castiel was a regular Angel in season four remember, and he got owned by Alastair, twice. Cain defeating Castiel does not necessarily put him at Seraph level. I'm not saying he's not, he just doesn't have the feats to put him there.