FunkMiller
Member
They're adapting Hickman's Secret Wars. Doom is the villain in that.
Most of the MCU has been based on Hickman's Marvel from S.H.I.E.L.D. being Hydra, Thanos' Black Order, etc. After Endgame they've been building to Hickman's version of Secret Wars (not the 80s version made to sell action figures). They introduced Incursions early on in Doctor Strange, literally showed a character stuck in a different universe due to an Incursion in Marvels, and both Loki S2 and Deadpool & Wolverine introduced the Molecule Man part of Secret Wars (with Loki replacing him) and then the MCU's version of Hickman's Anchor idea. In his Secret Wars, Molecule Man put a part of himself in each universe as an Anchor to hold them together. In the MCU, Loki is holding all of the universe strands together while each universe has an Anchor being who causes the universe to fade away after they die. I wouldn't be shocked if they made Iron Man be the 616 Anchor being in Secret Wars.
OK, but there's no reason to cast RDJ other than desperation to recapture the glories of the past. And it's a massive mistake to continue to lean on the multiverse bullshit. That explanation you've given is convoluted as fuck, and the general audience are not going to respond well. They'll love RDJ being back, until it starts to make zero fucking sense.