JLA/Avengers (Issues #2 and #4 are
titled Avengers/JLA) is a 2003-2004 crossover limited series published
by DC Comics and Marvel Comics, and features the two companies' teams of
superheroes, DC Comics' Justice League of America and Marvel's Avengers.
Publication history
In 1979, DC and Marvel agreed to co-publish a crossover series involving
the two teams, to be written by Gerry Conway and drawn by George Pérez.
Although work was begun on the series in 1981, editorial disputes
prevented the story from being completed.[1]
An agreement was eventually made between the two companies in 2002, with
the story to be written by Kurt Busiek and drawn by George Pérez. In a
joint panel at WonderCon 2000, Busiek, Avengers writer at the time, and
Mark Waid, then-writer of the JLA, stated they had nearly come to an
agreement to begin the crossover within the regular issues of their
respective books but the two companies could not come to a business
arrangement.
Avengers/JLA eventually became a 4-issue comic book mini-series jointly
published by Marvel Comics and DC Comics in late 2003 through early
2004. The mini-series was published in the 48-page Prestige Format.
Issues #1 and #3 were published by Marvel Comics under the title JLA/Avengers
while issues #2 and #4 were published by DC Comics with the title
Avengers/JLA. The entire story was reprinted by DC Comics in 2005 as a
2-volume collector's edition hardcover and then re-released as a trade
paperback in November 2008.
Plot summary
Krona, an exiled immortal from the DC Universe who gained the powers of
entropy, begins destroying entire universes in his obsession to learn
what happened before the Big Bang. The Grandmaster, an alien Elder of
the Marvel Universe who is obsessed with games, offers to tell Krona
about someone who has the knowledge he seeks; but only if Krona can beat
him in a game. The game involves manipulating the Avengers and the
Justice League into trying to obtain twelve items of power (six from
each universe - the DC items being the Spear of Destiny; the Book of
Eternity; the Orb of Ra; the Psycho Pirate's Medusa Mask; the Bell, Jar
and Wheel of the Demons Three; and the Green Lantern Power Battery of
Kyle Rayner; and the Marvel items being the Ultimate Nullifier; the Evil
Eye of Avalon; the Wand of Watoomb; the Casket of Ancient Winters; the
Cosmic Cube; and the Infinity Gems) that have been hidden around across
the two worlds. The New God Metron of the DC Universe also helps to
trick the heroes into competing.

Extra George Perez JLA Avengers Wallpaper
Numerous battles ensue, comparing and contrasting the powers and
personalities of each universe's heroes. The opposing teams continue to
skirmish until all of the items are gathered, at which point Krona and
the Grandmaster betray each other. Krona lethally blasts the Grandmaster
and scans his mind to learn of Galactus, while the Grandmaster uses the
power of the twelve artifacts to trap Krona between the two universes.
Krona breaks free and begins to merge these incompatible universes,
which would result in their destruction and the birth of another
universe. The Avengers and the Justice League join forces to battle
Krona, with a rapidly varying roster of characters and forms of
characters drawn from the entire histories of both teams. Krona is
finally defeated, and implodes to become a "cosmic egg". The two
universes are returned to normal with no evidence of Krona's tampering,
and the cosmic egg is later revealed to be monitored by the JLA.