The Marvel Book Expand Your Knowledge of a Vast Comics Universe by Stephen Wiacek

Devourer of Worlds
After millennia, something emerges with godlike power and insatiable
hunger. Ingesting the life-force of worlds, the being’s relentless passage
across creation leaves devastation in its wake: toppling ancient civilizations
and destroying embryonic planets. Intergalactic races learn to accept losses
to their territory or devise strategies and technologies to mask their presence
from this embodiment of inescapable doom known as Galactus, Devourer
of Worlds. This strange, cosmic colossus must constantly consume to
subsist. As time passes, Galactus recruits lesser beings to locate suitable
worlds for him. He imbues these heralds with a measure of his incalculable
power. When one—the Silver Surfer—leads him to Earth, the unimaginable
occurs. Galactus is defeated and driven away by the planet’s defenders.
The Earthlings repeatedly repulse Galactus, leading the major empires of
the universe to pay attention to this seemingly innocuous, fringe world. At
one point, Galactus almost starves to death, but is saved by the Fantastic
Four’s Reed Richards. The scientist deduces that Galactus is a vital
component of vast metaphysical processes that underpin existence, and that
all creation would suffer if he were gone. In truth, Galactus is a divinely
appointed cosmic agent of balance between Death and Eternity, and is
critical to the evolution of life itself.
Although unintentional, Galactus’ actions have huge consequences. After
he consumes Skrull homeworld Tarnax IV, the empire dissolves into civil
war. This leads to a fundamentalist religious revival and the Secret Invasion
of Earth by shape-shifting zealots who believe the world to be their
promised land. Having almost destroyed Earth so often, Galactus is
eventually targeted by the planet’s champions, the Ultimates. Their solution
to the Devourer’s never-ending threat is to overfeed him. This forcibly
evolves him from a creature hungry for planetary energies into a benevolent
voyager transforming dead planets into hospitable, life-sustaining worlds.