From March 1963 to October 1964, the Incredible Hulk wandered in the wilderness, both literally and metaphorically.
After his comic book ended with its 6th issue, he was a monster without a title.
But Stan Lee made skillful use of this tortured former protagonist as an antagonist against the Avengers, the Fantastic Four, Spider-Man, Thor and Giant-Man, and that move accomplished two purposes. It kept the Hulk alive in the minds of young readers, and it nurtured their growing sense of a vast, interconnected fictional universe, a Marvel universe.
Namor served the same function at the same time.
Rarely out of sight or mind, the Hulk returned in a new feature in Tales to Astonish 60. Drawn again by Steve Ditko, the Hulk was finally established in the form in which most people now know him — as a scientist turned into a monster by stress, anger, the fight-or-flight response.
Shared titles were necessary in Marvel’s expanding universe, and each of them had its own theme. Tales of Suspense featured the out-and-out superheroes, Captain America and Iron Man. Strange Tales featured two characters on the fringes of the superhero world, Nick Fury and Dr. Strange. And once Giant-Man departed, Tales to Astonish featured the Hulk and the Submariner, two super-antiheroes.