Nowadays, the multiverse and crises on infinite earths are universally accepted truths in Marvel Comics. However, in the 1980s, during the Bronze Age of comics, this was concept was revolutionary. One of the most pivotal events of the Marvel Comics canon was the Battleword storyline, the biggest crossover event of 1984–when pitting Marvel's still-growing roster of well-known heroes in a mass battle against their most famous foes, orchestrated by an enigmatic and terrifying figure in the shadows, known as the Beyonder.
Source：https://www.cbr.com/secret-wars-battleworld-1-review/
