Plot
The story of JLA/Avengers begins when Krona, the Maltusian who caused the original DC Universe to split into infinite realities, travels to the Marvel Universe seeking the truth of creation. There he meets The Grandmaster, who proposes they test their respective Universes against one another. Should Krona win, The Grandmaster offers to guide him to Galactus, the only being in the Marvel Universe to have witnessed the creation of existence . Should Krona's Universe lose, he is to spare the Marvel Universe from entropic destruction. Krona accepts, and the battle begins, pitting the Justice League of America (chosen to represent Grandmaster) and Avengers (representing Krona) against one another.