First Steps clip sees the Silver Surfer descend to Earth and issue a cryptic warning to the superhero group and citizens of the planet, heralding the arrival of Galactus. What happens in the new The Fantastic Four: First Steps clip?

In comics, Galactus is indeed a cosmic force of nature which is technically essential to the life-cycle of the Marvel Universe, in which planets die, new ones are formed, and new societies and empires rise and fall on a near constant basis across an infinite number of worlds.