Featuring over 30 superheroes from almost 40 movies released over the past 20 years, one would assume this December’s Avengers: Doomsday could be the ultimate Marvel Cinematic Universe final exam. 2019’s Avengers: Endgame was one thing, but since then, Marvel has introduced so many additional characters and concepts that the prospect of all of it paying off in a new Avengers movie is mindboggling. But, apparently, it may not actually matter. Speaking this week at SXSW London, Doomsday directors Joe and Anthony Russo referred to their upcoming film as being “Phase Zero” of the Marvel Cinematic Universe. “That serial shifting and changing and surprising you and then reinventing itself and then shifting and changing and then surprising you—that’s exciting and I think you’re going to see some shifting and changing [with Doomsday ],” Joe Russo said, via the Hollywood Reporter . “So, get ready for it. Look, we were with Rob [Downey Jr.] earlier today.…