Carter! Shiera
!
So I guess Nth-Metal provides some kind of connection to the "Dark Universe" which is supposed to be the main impetus of this event.
I wonder when that image of them in bed takes place? Is is present-day, or in the past? The narration makes it sound like it's from Carter's journal.
So doing work on another Earth is why Mr. Terrific hasn't been seen or heard from in so long...
Michael seems pretty keen on the idea of possibly releasing Joker from that box, so maybe it isn't Joker
?