The official trailer for "Avengers: Doomsday" has finally dropped, solving a nearly year-long mystery from the post-credits scene of "Thunderbolts*". In that scene, the New Avengers detected a multiversal ship entering Earth's atmosphere from their Watchtower headquarters. The vessel was identified as the Fantastic Four's "Excelsior," but the identity of its passengers remained unconfirmed.
The new trailer now confirms the ship is indeed carrying the Fantastic Four from "Earth-828," and they're not alone—Thor is with them. This reveal establishes a direct link between "Earth-616" and the Fantastic Four's home universe, suggesting Thor may have first traveled to Earth-828, alerting Reed Richards to the fact that multiple universes are beginning to bleed into one another and are on a collision course. To prevent this cataclysm, Mister Fantastic likely takes Thor's advice to seek assistance from the technologically advanced nation of Wakanda.
A scene previously unveiled by Marvel at a Shanghai exhibition also revealed that Reed Richards is studying the energy generated by the collision of different worlds. He is designing a so-called "Multiversal Cannon" to prevent these realities from destroying each other by continuously releasing energy. Since "Doomsday" is expected to involve the "X-Men Universe," Earth-616, and Earth-828, it's possible that a device will need to be built in each of the three worlds to stabilize the multiverse.
Meanwhile, Doctor Doom appears to be attempting to harness the universal collision for his own ends, aiming to merge different worlds into a single reality under his rule. The mysterious runes repeatedly seen around him could be used to absorb the energy released from these collisions, which would explain how he has become powerful enough to stop Thor's Stormbreaker.
"Avengers: Doomsday" is scheduled for release on December 18, 2026.