In Challange tab, you can choose to play Legendary Battle, World Boss and Shadowland.
Legendary Battle Edit
In Legendary Battle, you can recreating memorable scenes inspired by the Marvel Cinematic Universe and get bonus rewards by clearing stages.
World Boss Edit
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-8s sets and team to have a better chance at World Boss.
In Shadowland, fight your way to the top and collect various rewards.