Toward the end of his properly famous stint at Marvel as the architect of most of the mythology Jack Kirby became disenchanted with the business model which was limiting his ability to gain profit from his creations. As just an employee, he felt it was not in his best interests to continually add new creations to the Marvel Universe which he mostly populated for nearly a decade. So he stopped.
When Alicia confronts the new being he emerges from a great cocoon and uses his vast power to destroy his makers, realizing their evil intentions. The power of "Him" is robust and soon the Beehive is roiling and the scientists seek to escape.
Some prove more courageous than others, but all of them seemingly die as Him emerges in the final page and reveals himself to be a beautiful golden man brimming with power. As the Fantastic Four escape, Him brings down the Citadel and flies into space to find peace.
But his peace will be short-lived. More tomorrow.