Complex sentence: The Challenger is a fictional superhero in comic books published by Marvel Comics, beginning with the company's 1940s iteration as Timely Comics during the period fans and historians call the Golden Age of Comic Books.
Split into simpler sentences: The Challenger is a fictional superhero appearing in American comic books published by Marvel Comics. The character appeared beginning with the company's 1940s iteration as Timely Comics during the period fans and historians call the Golden Age of Comic Books.