Marvel Studios finally unleashed the first trailer for Avengers: Doomsday, and it's packed with the kind of massive reveals fans have been waiting for. The footage delivers an epic clash of heroes, teases a multiversal war, and offers our first real look at Robert Downey Jr. as Doctor Doom. But while excitement is running high, one particular detail has sparked an interesting conversation among Marvel fans. Throughout the trailer, Doctor Doom never removes his mask. If Marvel keeps that mystery intact throughout most of the film, it could make the character even more intimidating.