In New York City a giant structure appears in Central Park where many heroes investigate and are transported to Battleworld- a collection of different planets

Among the heroes are Spiderman, Iron Man, Hulk, Fantastic Four (minus Invisible Woman), Thor, Captain America, Captain Marvel (Monica Rambeau), She-Hulk, Hawkeye, X-men (Cyclops, Wolverine, Storm, Nightcrawler, Colossus, Prof X), and Wasp

Among the heroes is Magneto as well

Villains have also been  transported to Battleworld and they are Doctor Doom, Molecule Man, The Wrecking Crew, Absorbing Man, the Asgardian Enchantress, Ultron, Galactus, Doc Ock, Lizard, and Kang the Conqueror

A Cosmic Being known as the Beyonder makes himself known and claims he shall grant any wish to the side that eliminates their enemies

Doom factions out on his own to gain ultimate power after the villains, heroes, and Galactus (who also factions out on his own) refuse to ally with him  

Magneto also factions out on his own after the heroes oust him

Doctor Doom reprograms a comatose Ultron to follow his commands thereby taking leadership of the villains 

Magneto returns to the heroes location to cause a diversion to fulfill a plan and kidnaps Wasp in the process 

Spiderman discovers that the X-men plan to team up with Magneto but Xavier alters Spidey’s mind before he tells the Avengers 

Two other female villains transported to Battleworld join Doom and are given superhuman abilities and dub the monikers Titania and Volcana 

In a 2nd battle against the heroes, in which the villains lost the 1st, they gain the victory and the heroes are buried under a 150 billion ton rock 

Hulk holds up the rock from falling on the heroes 

Thor who had teleported out with Enchantress, who became a prisoner from the 1st battle, returns to face Doom. Doom orders Ultron to disintegrate Thor which is what seemingly occurs but survives

Doom eliminates Kang as well for attempted murder

The X-men convene with Magneto while Wasp escapes

The heroes get freed from under the mountainous rock and go to a nearby village for healing

X-men prepare for an offensive against Galactus as he brings his ship onto Battleworld 

The villains occupy the vacated heroes’ base. They notice Galactus’ ship

Magneto and Xavier attempt to discover Galactus’ plans by probing his mind but his mental defenses are too powerful

While Galactus is preoccupied, Doom sneaks aboard his ship where he finds Ulysses Klaw who ended up there as a transference of energy after the mutant Dazzler absorbed his essence and battled Galactus thus transferring him onto his ship. He joins the villains

Prof X sends Cyclops, Wolverine, and Rogue to a volcanic area because he telepathically deduced Doom and his cohorts planning to use it

Galactus begins construction on a machine to absorb the energy from the planet, Spider-Woman (Julia Carpenter) also turns out to be on Battleworld from Denver, and Wasp is fatally injured by an ambush from the Wrecking Crew

Galactus senses Doom on his ship and expels him from it

The Avengers go after She-Hulk who has gone to take vengeance on the villains for maiming Wasp

In Doombase (villain HQ) which the heroes have taken over, Spidey’s fate crosses with the symbiote that bonds with him and becomes his black suit as well as his future enemy Venom

Galactus begins his attempt to devour the planet’s energy and the X-men attempt to hold him off in lieu of the Avengers

Galactus absorbs his cosmic ship into his being instead then Doom takes his power by creating lenses from Klaw’s body and directing the energy through them

Doom then takes the Beyonder’s power

Doom massacres the heroes effortlessly

Mister Fantastic survives due to his molecular makeup and revives them

In a scuffle, Cap confronts Doom and then the surviving remnants of the Beyonder hiding within a possessed Klaw come out and reclaims his stolen energy from Doom

The Beyonder is gone as are Doom and Klaw and the story concludes with Mister Fantastic teleporting the heroes back to Earth, the Thing staying behind to figure why he reverts to human form whilst there, and the fate of the villains is ambiguous as they are last seen floating in space on a rock controlled by Molecule Man