Teased more than a year before it began in last year's Free Comic Book Day issue from the publisher, the battle sees The Question, The Phantom Stranger and Pandora's Trinity of Sin engaged in a massive, magical war in which the three Justice Leagues become entangled and...well, you can see.
And just like the last time we saw an iteration of this giant superhero melee, a new face appears in the background, with little explanation and few clues as to the identity of the mystery...hero?
That would be Doctor Light, a name and costume that's been taken by two individuals in recent memory. Dr. Arthur Light was a bad guy, best known for terrorizing the Teen Titans...until later in life, when it was revealed that he had once invaded the Justice League satellite and sexually assaulted Sue Dibny, the wife of the Enlongated Man, in Identity Crisis. Kimiyo Hoshi, a female, was an on-again, off again superhero for years, who played a major role in Crisis on Infinite Earths.
Whether this New 52 Doctor Light is one of those two--or another character altogether--isn't immediately clear, since s/he is so far away in the background (that's Light fighting Madame Xanadu). The character is slender, which isn't generally how superhero males are drawn, but flat-chested, which isn't generally how superhero women are drawn; s/he is in a scene with nothing but superheroes and Justice League members, which would point toward Kimiyo, but is wearing Arthur's helmet. The jaw doesn't have a beard, and seems more rounded than most comic book males, but there's none of Kimiyo's long hair to be seen under the helmet or framing the face.
It seems likely that, like The Atom, this is probably a new character being introduced and (like many presume was the case with Atom when the original drawing at left was presented) may not even have been identified by editorial yet by the time the cover was being drawn.