"Group Bosses are powerful enemies that cannot be defeated in one combat.To defeat a Group Boss, enlist the help of your friends. You can also help your friends by visiting their map.You'll earn silver for each combat, and Lockboxes when the Group Boss is defeated.Lockboxes contain a random prize, including a chance at winning a unique playable hero!Lockboxes can be opened in the Collections menu on the Flight Deck.Be sure you and your friends defeat the Group Boss before its timer expires, or it will escape and return later at full health!" — S.H.I.E.L.D. Intel