Keystone City, home of several Flashes, was terrorized by the gargantuan Marvel villain Terminus, and the Justice League of America stood in its path. Manhunter attempted a psychic probe, but "This being's mental shields are prodigious-- I can sense a mind within, but I cannot read it--!" Batman stood back, examining the bohemoth before determining its staff was its main power concern. The Dark Knight commanded Martian Manhunter to maintain the telepathic link amongst his team's members. Plastic Man covered Terminus' face shield with his body, forcing the gargantuan to unseal his helmet. This was just the opportunity the Manhunter needed. "I may not be able to sift through your thoughts, creature... but a full-strength telepathic bolt against your shields..." Meanwhile, Green Lantern Kyle Rayner redirected energy from Terminus' staff into its helm, seemingly slaying Goliath. It was swept away by the current bearer of the Spectre mantle, Hal Jordan. This of course unnerved Rayner, who succeeded Jordan as Green Lantern after he went mad and slew thousands, a sin for which he became the Spectre to atone. "We know how you feel, Kyle. Believe me, we know."
In the New York City of the Marvel Universe, the Avengers fought the classic JLA villain Starro. Meanwhile, Lobo visited the Sh'iar and Mongul the Brood.
At the Watchtower, J'Onn J'Onzz alerted, "Justice League. We have a visitor." This was the Watcher Uatu, who the Martian attempted to mentally contact in a variety of languages, but to no avail. Another intruder arrived, the Gamesmaster of the Elders of the Universe, who claimed the League would have to collect objects of power sprinkled through two universes in order to save them both. He was short on details, and when J'Onzz tried to scan him, he was dismayed. "For the third time today, my powers cannot reach into a mind that stands before me. It is beginning to grow annoying."
Though aggravated, Manhunter joined his team in following along with the premise and take a trip to Marvel Earth. J'Onn's party included Wonder Woman and the Atom, who sifted through the devastation of Genosha. "A scan of neighboring nations reveals these people were bombed for being genetic mutants. For the crime of being different." While Ray Palmer rested on a skull in his palm, Manhunter received the telepathic urging of the Batman, "Leave it, J'Onn. Move on." Batman failed to do the same in an off-panel confrontation with the Punisher, raising Plastic Man's ire (of all people.) Manhunter agreed, "...we can't let ourselves be distracted from our mission. People died in Keystone City. Our world is endangered, too." An assault by more giants, this time on Monster Island, were cause enough for further distraction. Manhunter took one off its feet with a blow, and the rest were handled in short order.
Atom located the first artifact, which was collected by Batman and presented to J'Onn J'Onzz for study. "Of course. I'll just probe... Great H'ronmeer! This-- this device, it-- the power it--" Manhunter's features began to distort as he tried to comprehend the scope of the Ultimate Nullifier. "--it alone could destroy... destroy entire universe..." The probe was fogging J'Onn's mind, which spread to the League, allowing Hawkeye the chance to grapple the device away with a custom arrow. Wonder Woman recovered it in time, while Iron Man blasted her team with an energy that forced her teammates' return to DC Earth.
Metron presented the Avengers with a Mother Box and the same mission as the League, whom they were confronted by upon travelling to DC Earth through a Boom Tube.
- On the cover, Martian Manhunter and She-Hulk are set together. This could be a nod to their match-up in the unpublished JLA vs. Avengers script from the early 80's, but I think it's just another instance of assuming all green people know one another.
- According to the Avengers/JLA Compendium: "The Martian Manhunter swears by H'ronmeer, a Martian deity (first mentioned in Justice League of America #256)."