Marvel has released the first full trailer for Avengers: Doomsday, offering the clearest look yet at Robert Downey Jr’s Doctor Doom and the collision of several corners of the Marvel universe.The footage brings together the Avengers, the Fantastic Four and characters from the original X-Men films, while hinting that they may not immediately see one another as allies.Ahead of the film’s release on December 18, here are five of the trailer’s most revealing details.1. Doctor Doom stops Stormbreaker with one hand Doctor Doom, played by Robert Downey Jr, stops Thor’s Stormbreaker in the Avengers: Doomsday trailer, offering an early demonstration of the villain’s power. Photo: Marvel StudiosInfoThe trailer quickly establishes Doctor Doom as a threat capable of challenging even the MCU’s strongest heroes.Thor descends through a surge of lightning and attacks Doom with Stormbreaker, only for the villain to stop the weapon with one hand. Doom does not appear to be knocked backwards or particularly troubled by the blow.It is a simple but effective demonstration of his strength. Stormbreaker was created in Avengers: Infinity War as a weapon powerful enough to kill Thanos, and Thor has since used it against gods, aliens and armies.Doom’s ability to halt it so casually suggests his armour provides far more than protection. In the comics, Victor von Doom combines advanced technology with formidable magical abilities, and the film may be drawing on both sides of the character.The scene also avoids revealing the full extent of his powers. Doom barely moves, making the encounter feel more like a warning than a proper battle.2. Steve Rogers is back – and can still wield MjolnirSteve Rogers, played by Chris Evans, reaches for Mjolnir as he reunites with Chris Hemsworth’s Thor in Avengers: Doomsday. Photo: Marvel StudiosInfoChris Evans’s Steve Rogers appears in the trailer’s closing sequence, where he reunites with Thor and reaches for Mjolnir.The moment recalls one of Avengers: Endgame’s biggest scenes, when Steve proved himself worthy of wielding Thor’s hammer during the final battle against Thanos.His use of Mjolnir in Doomsday suggests the returning Steve will be more than a retired soldier brought back to offer advice. He could once again become one of the Avengers’ most powerful combatants.It also adds another mystery. At the end of Endgame, Steve returned the Infinity Stones to their respective points in history, then remained in the past and grew old.The younger version in the new footage could therefore be the original character restored to his physical prime, or a version of Steve taken from another part of the multiverse. Marvel has confirmed Evans’s return, but has not explained where this version of the character has come from.3. Shang-Chi, Gambit and Mystique are drawn into the conflictGambit, played by Channing Tatum, clashes with Simu Liu’s Shang-Chi in one of the trailer’s unexpected battles between heroes from different parts of the Marvel universe. Photo: Marvel StudiosInfoThe presence of Shang-Chi, Gambit and Mystique is not itself a casting surprise. Simu Liu, Channing Tatum and Rebecca Romijn had all previously been confirmed for the film.What is unexpected is how directly they appear to be involved in its central conflict.Shang-Chi is shown fighting Gambit at the X-Mansion, while Mystique transforms into Yelena Belova during a confrontation with the real Yelena. Sam Wilson and Reed Richards can also be seen amid the disorder.For Liu, the film marks Shang-Chi’s first live-action movie appearance since Shang-Chi and the Legend of the Ten Rings in 2021. Tatum returns as Gambit after playing the character in Deadpool & Wolverine, following years of failed attempts to make a solo film.Romijn’s appearance carries even greater historical significance. She first played Mystique in the 2000 film X-Men, meaning Doomsday is drawing on more than a quarter-century of Marvel cinema.The clashes suggest the Avengers, Fantastic Four and X-Men may initially treat one another as threats. If the survival of one universe endangers another, the characters could also have genuine reasons to fight before confronting Doom.4. Loki remains at the centre of the multiverseThe New Avengers, Fantastic Four and Sam Wilson’s Captain America face Thor as Marvel’s different teams begin to converge. Photo: Marvel StudiosInfoTom Hiddleston’s Loki is briefly shown on the throne he assumed at the end of the second season of his Disney+ series.In that finale, Loki took control of the branching timelines, using his powers to prevent them from dying and becoming the figure holding the multiverse together.His inclusion in Doomsday was expected, but the trailer confirms that the film will directly revisit that role rather than treating the events of the series as optional background.Loki’s position makes him one of the few characters able to understand the full scale of a multiversal crisis. It may also limit his ability to join the fight, as leaving the throne could place the timelines at risk.His appearance suggests that the fate of the timelines will be central to the story.5. The heroes may have to decide which universe survives▶The trailer presents the crisis as something more complicated than simply defeating Doctor Doom in battle.Marvel’s description says heroes from three universes face an existential threat, while the footage refers to an “unthinkable decision”.That language points towards incursions and catastrophic events in which two universes collide. The concept was introduced in the MCU through Doctor Strange in the Multiverse of Madness and has long been associated with Marvel’s Secret Wars comic storylines.If two realities cannot coexist, the Avengers may be forced to decide whether one world must be sacrificed to save another. Such a choice would help explain why otherwise heroic characters are fighting at the X-Mansion and why the film brings together teams from separate universes.It could also shape Doom’s role. Rather than simply trying to conquer Earth, he may offer a ruthless solution that the heroes consider unacceptable, even if it preserves part of the multiverse.Avengers: Doomsday will be released in cinemas on December 18