The first official trailer for Avengers: Doomsday has confirmed that the film is adapting "Time Runs Out," one of the most acclaimed and devastating storylines in Marvel Comics history. The trailer gives fans their first glimpse of Robert Downey Jr.'s Doctor Doom and shows the Avengers, Fantastic Four and X-Men appearing together on screen for the first time, alongside dialogue and imagery echoing the comic's apocalyptic tone, including Doom's warning of an "unthinkable decision" ahead.

Written by Jonathan Hickman, "Time Runs Out" depicted the final days of the Marvel Universe as it faced "incursions" — multiversal collisions between parallel Earths — pitting Iron Man and Mister Fantastic's Illuminati, Captain America's Avengers, and Namor's Cabal against one another over how far to go to save their world. The storyline is built around themes of sacrifice, encapsulated in Hickman's line "One was life. And one was death," and is expected to raise personal stakes for characters such as Reed Richards and Sue Storm, whose son Franklin is in danger, and Thor, protecting his daughter. Directors Joe and Anthony Russo, who previously delivered Avengers: Infinity War's landmark ending, appear to be aiming for Doomsday to be even more emotionally devastating ahead of its follow-up, Avengers: Secret Wars.