Crisis on Infinite Earths

"Crisis on Infinite Earths" is a major crossover event in DC Comics where multiple universes—comparable to different realities—are threatened by a powerful villain, Anti-Monitor. To save the multiverse, heroes from various worlds unite to confront this threat. The event results in significant changes, including merging the different universes into a single, unified reality. It serves as a storytelling reset, allowing new directions for characters and series, and is considered a landmark in comic book history for its scope and impact on DC's continuity.