In Challenge tab, you can choose to play Legendary Battle, Squad Battle, World Boss, Shadowland and Timeline Survival.
In Legendary Battle, you can recreate memorable scenes inspired by the Marvel Cinematic Universe and get bonus rewards by clearing stages.
In Squad Battle, you earn higher Battle Points to claim victory against other players.
World Boss are the End Game content of MFF. You need at least 1-3 6* heroes to participate in them. They are hard in the beginning, but with the right combination of heroes and team soon you'll be a pro at finishing them. It is advisable to use high level geared heroes with good ISO-8 sets and team to have a better chance at World Boss.
In Shadowland, fight your way to the top and collect various rewards.
In Timeline Survival, defeat the villains in your timeline and earn great rewards.
In Dimension Rift, clear it on higher difficulties to get awesome rewards.