Batman / Superman #13 (variant card stock cover - Mark Brooks)

What happens when the Dark Knight and the Man of Steel wake up on a skull-shaped planetoid packed full of cybernetic versions of their entire rogues galleries? Figure out why they're being worshipped like gods, that's what! What is this strange new Brainiac's endgame-and how did Batman and Superman's own villain database mutate into this twisted, metallic death planet? The mystery deepens as our heroes' allies desperately search for their missing comrades...