You were here for the big fight, Lucifer and everything? You were here with his being a jerk to everyone on here? That was an archangel. SO yes, you have seen one, and we weren't able to put him down for good.
Opening it is less of an issue than getting the means to.
Jesse and people like her are the reason this is even being considered. I personally don't want Lucifer freed, and that's their endgame here. I'd rather it not be an option for them