There are multiple "Secret Wars":

• Secret Wars (1984): Marvel's first crossover event. The Beyonder kidnaps various heroes and villains to fight at Battleworld.
  • Secret Wars II: Continuation of the Beyonder's story. The Beyonder takes physical form and visits Earth.
  • Secret Wars 3: Continuation of the Beyonder's story. The FF and Doctor Doom visit the Beyonder's universe.
• Secret Wars (2015): The Beyonders destroy the Multiverse, but Doctor Doom steals their power to save a small portion: Battleworld.

They all involve the Beyonder(s) and the Molecule Man. Doctor Doom is usually important, except in Secret Wars II. Twice, he steals the power of the Beyonder(s) and takes over a patchwork planet called Battleworld.