Avengers: Doomsday is the kind of cinematic experience that warrants a big lead-up, and thanks to Avatar: Fire and Ash, it’s getting one. But the third trailer finally delivered what fans have been waiting for: the X-Men. Ian McKellan returns as Erik Lehnsherr in the new Avengers: Doomsday trailer. Marvel StudiosThis may be a teaser, but it’s no tease: these characters are well and truly canon, and will interact with everyone else in Avengers: Doomsday. Avengers: Doomsday premieres in theaters on December 18, 2026.