Los Angeles, July 20 -- And the wait is over. The official trailer of Robert Downey Jr.-starrer 'Avengers: Doomsday' was unveiled on Monday evening.

The trailer shows the Marvel heroes assembling as Doctor Doom prepares to wreak multiverse-crossing war on the heroes. Thor faces off against Doom and also reunites with Chris Evans' Captain America, making his long-awaited return to the MCU after "Avengers: Endgame." Several of Fox's "X-Men" characters also officially cross over into the Avengers' universe, including Professor Xavier, Magneto, Mystique, Cyclops and Channing Tatum's Gambit from "Deadpool and Wolverine." After hitting the big screen last year, the Fantastic Four and Thunderbolts are also back to help the Avengers save the mul...