There was a back-up story at the end of Justice League #6 by Geoff Johns with art by Carlos D'Anda featuring Pandora and the Phantom Stranger. It seems little Pandora not only opened a box long ago, but recently realigned/strengthened the DC Universe. She is doing all this to have her curse lifted. The Phantom Stranger was sent by the Circle of Eternity to warn her that she must not involve herself only observe, and to take the box from her. Pandora doesn't take this very well and puts a mystical bullet in The Phantom Strangers head. This of course doesn't kill him and she tells him to stay away or she will tell everyone who he really is and then their will be a lot of people gunning for him. Pandora needs to find The Strange and she is going to have the Justice League help her do that, even if they don't want to.
This little back-up makes you want to read even more, go back and check out what you have read, and wonder what is in store for the "New Rejiggered 52" from this point forward. From what I have heard and read you will have to check out DC's Free Comic Book Day issue for more on Pandora and the "New Rejiggered 52", and also follow Pandora's exploits in the Justice League. If you are like me you can't wait.
Oh and who is the third sinner that The Phantom Stranger mentions? Cain? That would be my guess, but with most of the what has been happening in the DC Universe we will just have to wait and see. I'm okay with that.