From the publisher's website:

Marvel Legendary® Secret Wars is the Second Big Box Expansion since the Dark City release! For the first time ever players can now play AS the Mastermind against the other players. Build your team to dominate as you battle against various universes in Battleworld. Secret Wars features playable characters from the Illuminati, Cabal and favorites from alternate universes. Work both with - and against - other players to defeat the various Battleworlds while laying waste to planet Earth. Find 14 new Heroes, 5 new Masterminds, 6 new Villain groups, and 8 new Schemes. **This is not a standalone product, Legendary®: A Marvel Deck Building Game required to play.**