The Russo Brothers have revealed that Avengers: Doomsday will mark a “phase zero” reset for the Marvel Cinematic Universe, with Robert Downey Jr returning in a major new role as Doctor Doom.

Speaking at SXSW London 2026 during a session titled Building Artistic Universes Without Borders, directors Anthony and Joe Russo discussed their return to Marvel and the creative direction of the upcoming film. Joe Russo described the project as a complete creative restart, saying, “This is starting over from scratch,” and adding that the goal is for the film not to rely heavily on past MCU storylines.

The filmmakers said the idea for Avengers: Doomsday emerged after discussions with writer Stephen McFeely, whose concept reignited their interest in returning to the franchise following Avengers: Endgame. Anthony Russo noted that while Endgame felt like a conclusion, the new story opened up “all new kinds of possibilities.”

Joe Russo also confirmed that Robert Downey Jr, best known for playing Iron Man, will now appear as the antagonist Doctor Doom. He explained that the team is “back to phase zero of the MCU,” emphasising reinvention, unpredictability and a fresh narrative approach.

The Russos also reflected on managing large ensemble casts, highlighting the importance of balancing character perspectives in expansive superhero storytelling. Joe Russo added that each character must be treated carefully to avoid disappointing fans invested in the franchise.

Beyond Marvel, the directors discussed the evolving film industry, praising digital platforms and independent creators for reshaping modern storytelling. They argued that audiences should have freedom in how they consume content, whether in cinemas or online.

Avengers: Doomsday is expected to premiere in December 2026.