Doomsday theory explores how the Fantastic Four might travel to Earth-616. It suggests Reed Richards uses Galactus’ ancient ship tech, combined with his own inventions, to build multiversal transport and rescue Franklin Richards from Doctor Doom’s grasp.

First Steps" has a thrilling ending that teases Dr. Doom and where the MCU goes from here in "Avengers: Doomsday."

First Steps' includes two post-credits scenes. Here's how that big reveal sets up what's coming in Phase 6 of the MCU.