The cover to Justice League issue 18 gives us a lot of little bits of information. For one thing, it's our first view of the "Grid", which Geoff Johns teased in Justice League issue 12 as the key to expanding the Justice League. Furthermore, it was revealed that one of the new recruits would be a traitor. Could the traitor be on the cover? My best bet for who the traitor is would be Element Woman. She was depicted as being very sweet in Flashpoint but also as off her rocker. On top of that, the Orb of Ra that gave Metamorpho his powers was stolen from the Black Room by David Graves in his campaign against the Justice League (see the 2012 Free Comic Book Day Issue and Justice League issue 7). You can see the elemental rod next to David Graves's book in Justice League issue 7. We could very well be seeing an updated version of the Judas Contract.
As for motives, not only does David Graves hate the Justice League, he's also working for Amanda Waller now (Justice League 12). And she really doesn't trust the Justice League. Furthermore, the US government wants a spy on the Justice League (Justice League 8).
JUSTICE LEAGUE #17
Written by GEOFF JOHNS
Art and cover by IVAN REIS and JOE PRADO
Variant cover by STEVE SKROCE
1:100 B&W Variant cover by IVAN REIS and JOE PRADO
On sale FEBRUARY 20 • 40 pg, FC, $3.99 US • RATED T
• The epic, full-length conclusion to "THRONE OF ATLANTIS" hits as Aquaman and the League make a sinister discovery that changes both the outcome of the war and the future of the Justice League!
• What is THE GRID—and what does it mean to expanding the Justice League?