Galactus is a fictional character appearing in American comic books published by Marvel Comics. Formerly a mortal man, Galactus is a cosmic entity who originally consumed planets to sustain his life force, and serves a functional role in the upkeep of the primary Marvel continuity. Galactus was created by Stan Lee and Jack Kirby and first appeared in the comic book Fantastic Four #48, published in March 1966. Lee and Kirby wanted to introduce a character that broke away from the archetype of the standard villain. In the character's first appearance, Galactus was depicted as a god-like figure who feeds by draining living planets of their energy, and operates without regard to the morality and judgments of mortal beings. Galactus' initial origin was that of a space explorer named Galan who gained cosmic abilities by passing near a star, but writer Mark Gruenwald further developed the origin of the character, revealing that Galan lived during the previous universe that existed prior to the Big Bang which began the current universe. As Galan's universe came to an end, Galan merged with the "Sentience of the Universe" to become Galactus, an entity that wielded such cosmic power as to require devouring entire planets to sustain his existence. Additional material written by John Byrne, Jim Starlin, and Louise Simonson explored Galactus' role and purpose in the Marvel Universe, and examined the actions of the character through themes of genocide, manifest destiny, ethics, and natural/necessary existence. Frequently accompanied by a herald (such as the Silver Surfer), the character has appeared as both antagonist and protagonist in central and supporting roles. Since debuting in the Silver Age of Comic Books, Galactus has played a role in over five decades of Marvel continuity.