The "Doomsday" plot leak also seems to confirm the big fight at the X-Men mansion in the universe where Monica Rambeau ended up at the end of "The Marvels." That universe's anchor being is a Professor X (Patrick Stewart) variant that Doom wants to kill. Interestingly, Earth-616 and Earth-10005 -- where Monica is -- are on a collision course.

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

This story discusses major plot developments, including the ending and post-credits scenes, in "The Fantastic Four: First Steps," currently playing in theaters. From the very first scene, the question of what will become of the child of Reed Richards (Pedro Pascal) and Sue Storm (Vanessa Kirby) looms over "The Fantastic Four: First Steps.