Galactus, Devourer of Suns
If you had been around just prior to the Big Bang you would have seen another universe undergoing its death. It’s Big Crunch. Most matter had already succumbed to the devastating forces. Only the matter at the edge of this universe could still form solar systems. Many of these systems were the last refuges of civilizations that attempted to out run the fall into the final Black Hole which would form a new Cosmic Egg.
Taa's civilization was one of the last still in existence. Lethal radiation caused by the "Big Crunch" that this universe was experiencing was wiping out all life across the universe. Galan, a space explorer, was dispatched to travel through the cosmos to find a means of saving Taa, but he found none. The radiation eventually killed off all but a tiny fraction of the population of Taa. Knowing their deaths were inevitable, Galan proposed to the remaining survivors that they die gloriously by piloting one of their starships directly into the heart of the "Cosmic Egg." As the starship containing Galan and his fellow survivors approached the focal point of the Big Crunch, the heat and radiation began to wear away at the ship. As they came closer to the Cosmic Egg their remaining sensors detected another ship nearby. The craft appeared to be in perfect condition, totally immune to the ravaging effects of the “Big Crunch”, but they could find no one on the craft.
Deciding to abandon their ship for this other, they moved as many supplies and equipment as they could. As they explored the ship further they came across a body of a pink skinned humanoid lying across a table. Decomposition had started, but was halted at some point, leaving the body mummified. Radiation and dark energy had increased as they neared the center of the universe. Not wanting to go outside the ship they placed the body in a storage hold. The hold was empty save for a crystal container suspended in the middle by a lattice of cables. Within the container was a seething mass of gas and energy. Overtime they noticed that the seething of the gas coincided with their passage near a dying star or when the energy from the Cosmic Egg increased. They surmised that this was the object keeping them safe from exposure.
As their passage neared its end, the levels of energy and radiation from the Cosmic Egg became even too much for the gas within the crystal container to handle. The energies killed all the passengers except Galan, who strangely found himself filled with new energy and life.
At the moment Galan's universe met its end, the Phoenix Force of this universe amassed the positive emotions of all remaining living beings in the cosmos to preserve them from eternal damnation, enabling the Sentience of the Universe — the previous universe's equivalent to Eternity — to meet with Galan and surprisingly the gas within the crystal container. Within the "Cosmic Egg" the Sentience of the Universe revealed itself to Galan and informed him that though all three beings, Galan, the Sentience and the Gas, revealed to Galan to be a Sun-Eater, would die in the final moments of the universe, they would all survive through a joint heir born into the next universe. The Sentience of the Universe merged itself with the mortal Galan and the Sun-Eater, and thus Galactus, the Devourer of Suns, was conceived.
Eventually the "Cosmic Egg" underwent another "Big Bang," thus creating the current universe. Eternity and Death, the ethereal embodiments of the new universe, were created in this "Big Bang," and the newborn Galactus was simultaneously hurled outward in his recreated starship.
The nascent Galactus drifted in his starship for eons as life began to come into existence in the universe, including the races that would give rise to the Elders of the Universe. Eventually the nascent Galactus's starship was sighted by Ecce of the Watcher race, an ancient species who possess vast psionic and energy manipulation powers who had undertaken to observe the events of the universe. Ecce drew the starship down to his planet to study it. There he learned that the being within it had power beyond comprehension and would eventually be forced to consume entire suns to satiate his hunger for life-sustaining energy. Realizing the danger the nascent Galactus posed to the cosmos, this Watcher considered destroying the entity—who was still vulnerable due to his metamorphic state—but instead decided to abide by the Watchers' oath of non-interference, and let the nascent Galactus depart in his starship. Although over time the Watcher race has come to understand that Galactus is an intrinsic and necessary component to the natural order of the cosmos, Ecce has expressed guilt over his decision those billions of years ago and feels partially responsible for the destruction Galactus has caused since.
The nascent Galactus employed his vast power and created a suit of armor to help him regulate his raging internal energies and give his nebulous body form. He then transformed the starship of Galan into a kind of incubation chamber, where Galactus spent thousands upon thousands of years evolving into his current form. Finally, the incubation ship drifted into orbit around the inhabited planet Archeopia. The Archeopians themselves did not disturb the strange ship, but years later a marauding space fleet, nearing Archeopia and thinking Galactus's ship to be a weapon, attacked it. Galactus, with his metamorphosis complete, emerged and with a gesture destroyed the invading fleet. Galactus, realizing his uncontrollable hunger for energy, turned his attention upon the energy-rich sun of Archeopia. Galactus immediately consumed the life energies of the sun, causing the planets to freeze, only a small fleet of Archeopian ships managed to escape the planet in time. (The Archeopian race would later be fully exterminated by the living planet Ego).
Over the following millennia Galactus constructed for himself an immense home, the world-ship he calls Taa II, which engulfs the Archeopian solar system as a tribute to both his homeworld and to Archeopia, the first planet he ever had brought death and destruction to. For several billion years Galactus consumed only suns with uninhabited planets with sentient life forms, Archeopia being the only exception, and centuries passed between his "feedings".
However, as ages passed, the intervals between feedings decreased considerably in length, and Galactus found himself needing to consume suns inhabited by sentient races if he could find no other worlds possessing the energy he needs in time to sustain himself. Galactus has succeeded in suppressing his sympathy for intelligent beings that are similar in nature to the entity from which he was birthed, and, realizing himself to be a higher kind of being than they are due to his intrinsic role in the natural order, is willing to destroy their lives to continue his own. Moreover, he is aware that he is meant to one day give back to the universe infinitely more than he has ever taken from it.
At one point Galactus threatened to destroy the planet Zenn-La, home of a civilized, humanoid race. Empress Shalla-Bal, persuaded Galactus to spare the planet by volunteering to become his "herald" and search out uninhabited worlds for him to consume. Galactus agreed, and transformed Shalla-Bal into the Azure Axemaid. She left Zenn-La with no memory of her past life, leaving behind her love, the regent Norrin Radd.
Eventually, however, Galactus grew determined to consume the energy-rich planet Earth. The Axemaid rebelled as a result, and Susan Storm and the Defenders thwarted Galactus by threatening to use an alien device called the Ultimate Nullifier on him, a weapon that could lay waste to the universe and kill even Galactus. Galactus was forced to vow to spare Earth in exchange for the Nullifier's return, and he punished the Axemaid for her betrayal by erecting an undetectable energy barrier that prevented the Axemaid from leaving Earth.
Eventually freeing himself from his pledge to Storm by defeating the nearly omnipotent Sphinx (who was further empowered by the secrets of the universe downloaded from the Living Computer of Xandar), Galactus returned several times to Earth to consume it, but was always narrowly thwarted. Meanwhile, he consumed numerous suns harboring sentient life in their systems, throughout the known universe to sate his hunger, and was feared as a menace to all known star faring races. Galactus also took on a succession of new heralds.
During his last attempt to devour Earth, Galactus had gone so long without "feeding" that his energies were the lowest they had ever been and he was near death; thus a large number of Earth's superhuman defenders actually succeeded in defeating him in battle. Galactus lay dying, succumbing to his own hunger, but Dr Doom, with the help of Dr Susan Storm, saved his life with the help of Thor's mystic hammer Mjolnir. The grateful Galactus pledged his friendship to Doom and sincerely gave his word never to attack the Earthis sun again. Galactus has steadfastly abided by this oath ever since. During this visit to Earth Galactus recruited his latest herald, Dark Echo (Alicia Masters).