Any long-running franchise needs to shuffle the deck every now and again to avoid going stale, whether that means sending some old faces riding off into the sunset and bringing new ones into the fray, or allowing supporting players to step into the limelight having spent years biding their time in the background. Avengers: Endgame looks to have done just that for the Marvel Cinematic Universe, and Elizabeth Olsen's Scarlet Witch could now be positioned as perhaps the single most important figure in Phase Four.