Synopsis
On Polemachus the Imperion Arkon is relaxing with his consort Thundra when his Vizier tells him of a huge pair of burning eyes that have appeared in the sky. A voice resonates in everyone's heads demanding to know the truth about the secret. When it gets no answer it destroys the whole universe containing Polemachus.
In another universe the Weaponers of Qward are attacked by the Crime Syndicate Of Amerika. But then the eyes appear again, ask the question and then destroy *this* universe.
Eternity is seen holding a galaxy in Marvel Earth's universe. The gambling-addicted Elder Of The Universe called Grandmaster is also observing that galaxy to see the outcome of a age-old bet he made with another of the immortal Elders. Then the eyes pop up and the voice blasts En Dwi Gast's mind. But the Elder senses that the mental probe will destroy the universe and halts its progress. The eyes materialise further into a humanoid being who announces himself as Krona seeking the Ultimate Truth.
1 month later in the DC Universe The Justice League Of America (Aquaman, Flash (Wally West), Green Lantern (Kyle Rayner), Martian Manhunter, Plastic Man, Superman and Wonder Woman) are fighting a huge robot (that Marvelites would recognise) called Terminus, trying to stop it reaching Metropolis. Batman is keeping out of the battle studying the foe. He suddenly announces that its power is in its staff that emits force blasts. Via a mental link provided by Manhunter he directs most of the team in a concerted attack on the enemy while Lantern strikes at the staff. Terminus believes they are trying to steal the staff, but instead GL creates a Power Ring object which funnels the staff's blast back at its owner who is then blown to bits.
Just then Spectre (Hal Jordan) appears briefly and sends Terminus back to the universe it came from. The League are still not used to Hal's new role, but they settle down to rescuing civilians from the debris of the fight.
At the same time on Marvel Earth DC's Starro The Conqueror has appeared over Manhattan and the giant starfish drops loads of little Starros which attach themselves to people's faces to take them over. The Avengers (Captain America, Iron Man, Jack Of Hearts, Quicksilver, Scarlet Witch, She-Hulk, Thor, Triathlon, Vision, Warbird, Wasp and Yellowjacket) are on the case but She-Hulk, Triathlon and Yellowjacket have already succumbed. Then the Starros get Thor and things look really bad.
Wanda Maximoff helps Carol Danvers get the parasite off her brother Pietro's face. Freed Quicksilver tells them all the hosts are mentally connected to each other and Starro, who only wants to gain total control and bring total order. This gives Vision an idea based on Wanda's Chaos Magic. He places Pietro's starfish on his ex-wife's face. As Starro takes her over she channels a mega-amount of Chaos Magic into the foe, who flees screaming into space.
All the little Starros fall dead, and everyone is free. Scarlet Witch reports that the Star Conqueror came from another universe, but it doesn't know how it got here. Vision gets a transmission from Quasar in the Deep Space Monitoring Station. It appears that there are lots of other attacks by unknown beings. We see DC's Lobo fighting the Imperial Guard in Shi'ar space, and the Aakon being attacked by Khunds. His Q-Scan reveals that they are all from the same other universe as Starro. Wasp suggests to Iron Man that they need a way of detecting if any more similar visitors appear on Earth.
Meanwhile on DC Earth Flash has a piece of Terminus' armour it left behind. He's detected the vibrational frequency of its home universe and is tuning his Super-Speed to it. He encounters great resistance but then breaks through the barrier, and loses mental contact with J'onn J'onzz ....
... and finds himself in a pleasant little town which must occupy the place on this Earth where his own Keystone City lies. He starts scanning but is interrupted by an angry mob chasing a boy named Pete Gehringer who has just manifested his obvious mutant appearance. Wally West tries to stop them but they assume he's 1 of Magneto's Evil Mutants come to recruit Pete. Flash tries to use his power to hold the crowd back but finds there's no Speed Force in this universe for him to access. Pete escapes with mighty leaps, and Wally is left at the mercy of the mob.
In their Watchtower on the Moon the rest of the JLA have also detected more intruders into *their* universe. We see Thanagarians fighting Skrulls, and Mongul facing a horde of Brood. Then a worse-for-wear Flash contacts them to say that his fading powers meant his vibrational rate reverted to normal and he popped back to Keystone City. His report of the mob attacking a kid suggests this other world isn't a nice place.
Then an alarm alerts them to a presence outside. Flash super-speeds to the Moon. We see Uatu hovering outside the Watchtower. Martian Manhunter senses only curiosity, but the giant being won't communicate. Then Superman senses another intruder who walks through their walls. It's Grandmaster who tells them that the Watcher is only here to record a momentous event. Green Lantern fashions a force-cell for the new guy and Superman asks him what he wants. GM admits that he is from the same universe as the invading threats, but he likes things to be fair so he's come to tell them what's going on. J'onn can't read his mind but En Dwi Gast allows Wonder Woman to bind him with the Lasso Of Gaea which compels the truth.
He tells them that the barrier between their universes has been weakened by someone. Things will get worse and the end result may be the destruction of both. He claims that the only way to stop the process is to assemble 12 items of power, 6 from each universe. He shows them the 12, and various of them recognise their 6:- The Bell, the Wheel and the Jar (count as 1). The Medusa Mask. The Spear Of Destiny. The Eternity Book. The Orb Of Ra. Green Lantern's Power Battery. (Many Marvelites will recognise the other 6, but we'll come to them later.) He refuses to answer any more questions, but mentally gives them the locations of all 12 and tells them that others will be after them also. And then Grandmaster disappears.
The JLA are sceptical. Diana says her lasso convinced her was telling the truth but not all the truth. They agree to go investigate this other Earth that Flash found unpalatable. Flash himself will stay behind because his power doesn't work there. Atom will take his place. But it is Flash who uses his vibrational tuning to send them across the dimensional barrier. And the Watcher continues to watch.
In Avengers Mansion Tony Stark has created a scanner for the energy data of the invaders (working from Quasar's data and a scan of Starro by Jack Of Hearts). Captain America has put out a call for non-current team members and Hawkeye turns up. (Janet van Dyne greets Clint Barton with a kiss on the cheek, months before their affair near the end of this series.) Stark's alarm goes off ...
... as the JLA arrive in the Marvel Solar System, passing the ancient ruins in the Blue Area Of the Moon - but they have no time to investigate that. They enter the atmosphere and split up. Aquaman and Green Lantern see the populace of Latveria forced at gunpoint by Doombots to cheer Dr Doom. Atom, Martian Manhunter and Wonder Woman see the evidence of mutant genocide on Genosha beneath a towering statue of Magneto. Superman sees Hulk gorging himself after fighting the army in Michigan. Batman and Plastic Man see Punisher shooting drug dealers in New York. Bats takes time out to beat Frank Castle up. When they reconvene Superman declares that the heroes of this world have let it go to hell. He doesn't trust them with the items of power so the JLA must find them and take them away.
There 1st location is an island in the Sea Of Okhotsk. But it is Monster Island and they are attacked by Fin Fang Foom, Giganto, Tricephalous and Vandoom's Monster among others. While most of the team deal with the monsters, Batman tries to slip between them to get to the target but little Atom gets there 1st. J'onn J'onzz detects that this artefact alone could destroy the universe (we know that it is the Ultimate Nullifier inside a force globe). But then an arrow from Hawkeye knocks it out of Manhunter's hands. And a device in the hands of Iron Man sends the JLA back to their own universe. But at the last instant Wonder Woman grabs the arrow and the Nullifier. The JLA return to the Watchtower determined to rescue the other 5 items from that dangerous world.
Captain America, Quicksilver, Scarlet Witch, Thor and Vision are also on Monster Isle. Vision detects someone watching them but when they investigate they are repulsed by a force field. Then Metron of the New Gods reveals himself on his Mobius Chair. He claims to be here only to observe (like Watcher) but he tells them about the Justice League and the 12 items of power. Now it's the turn of our team to recognise their 6 - as well as the Ultimate Nullifier they are the Cosmic Cube, the Evil Eye, the Casket Of Ancient Winters, The Soul/Infinity Gems and the Wand Of Watoomb. He claims that the Avengers must stop the JLA from acquiring them or their universe will die. Atom avoided being sent home and is listening, and he realises this isn't exactly what Grandmaster claimed. Before leaving Metron gives them a Mother Box to get them to JLA's Earth ...
... and they arrive through a Boom Tube in Metropolis to interrupt a bank robbery by a gang led by Loophole. After they defeat them they are mobbed by a horde of superhero fans. (A fan asks them if they're members of the JSA because they're too old to be JLA or Titans. I guess this is an in-joke because the Avengers *have* been around longer than the post-Crisis JLA.) Cap drags them away and they see other evidence of superhero worship in news items - not just Superman and Wonder Woman but Booster Gold, Supergirl and the JSA Flash (Jay Garrick) (and Lex Luthor's in the news too). But Cap looks at the futuristic city and jumps to the conclusion that the superheroes built it and now demand adoration from the public (like Dr Doom).
Then 8 JLA (including Flash but not Atom) turn up to 'greet' the 7 Avengers. Something has been niggling at the back of Hawkeye's mind and now he realises what it is - these guys are Squadron Supreme knock-offs. (The Squadron of course were originally designed as a version of the Justice League.) And he also figures they're probably being mind-controlled as usual. Captain America and Superman take uncharacteristically belligerent stances. Some of their team-mates try to talk them down but Thor starts the fighting by throwing Mjolnir at Supes.
Elsewhere Grandmaster and Metron are observing the events. It appears that GM is playing 1 of his games with Krona as an opponent. Metron points out that if Krona loses he'll probably just do what he wants anyway. En Dwi Gast agrees that both universes may well die in the end. But the game gives him time to implement his true plan.
And Atom has hitched a ride on Metron's dimension-spanning Chair and overhears the whole thing.