Set is one of the Elder Gods, the first beings on Earth, spawned by the sentient Demiurge biosphere shortly after the world had cooled. Already mighty, Set spawned offspring such as Sligguth and Damballah to expand his control of Earth. Seeking further power, Set consumed the centaurian Elder God Hyppus and absorbed his life energy, becoming Earth's first murderer and initiating his descent from true god to demon; other Elder Gods imitated Sets tactics, leading to massive slaughter. Wishing to stop this, the Elder Goddess Gaea birthed Atum, who became Demogorge and banished or slaughtered most of the Elder Gods. Set joined with his brother Chthon against Demogorge but they were overpowered, and Set and his spawn were among those forced to leave Earth; Set left behind illusory forms of himself and his progeny to fake their deaths. Maintaining ties to his home from his self-created extradimensional realm, during the Mesozoic era, Set created a mystical affinity with the dinosaurs that evolved on Earth. Set absorbed the life energies released by their violent killings, amassing enormous power over millions of years. During the late Cretaceous period, Gaea, the sole Elder God allowed to remain on Earth, realized that the dinosaurs had reached an evolutionary dead end and that they were preventing mammals from evolving to their full potential,so she shifted her attention to them, intending to permit the extinction of dinosaurs in favor of mammals. Unwilling to lose his power source, Set ordered the dinosaurs to destroy all mammals. Gaea challenged Set to face her, and Set's spirit appeared on Earth in his first true physical form as a giant serpent created by fusing the bodies of three dinosaurs. Having underestimated Set's power, Gaea called upon her son Atum who battled Set, cutting off his head in the process. Set regrew two heads for each one severed until he had seven, but during their lengthy battle, nearly all of Earth's dinosaurs were destroyed — by numerous causes, some of which were the direct result of the battle — except for an isolated few in areas such as the Savage Land. With Set thus weakened, Atum (who had transformed into Demogorge during the struggle) broke Set's influence over the Earth. As a result, Set, who thereafter retained seven heads, could not return to Earth unaided. Set could, however, manifest in the forms of Tiamat and other dragons or serpents to maintain his influence on evolving religions, thus deriving further power.
Approximately 1 million years BC, Sligguth spawned the Serpent Men, reptilian humanoids serving as Set's agents on Earth, and the similar-looking Dragon Kings. Set's other children include Ishiti, who begat the Man-Serpents with snake-like bodies and human heads adorned with snakes in place of hair; Phorcys, who begat Echidna, the parent to the giant, magically-powered Snakes of Many Colors and many monsters of Olympian (Greek) mythology; the cosmically powerful Dragon of the Moon; Tartessus, progenitor to the Snake Clan; and Yamato-no-Orichi, the eight-forked serpent of the Kami (Japanese gods). A pair of early Serpent Men, granted increased intellect by Set, infiltrated a verdant haven created by the time-traveling sorcerer Sise-Neg for a pair of pre-human anthropoids. Descendants of these humanoids visited the haven annually as part of their tribe's migration, and the tribe leader and his mate encountered the Serpent Men (disguised as anthropoids) who tried to convince them to worship Set, offering warmth and protection in exchange for slaying their own tribesmen as food for Set, and bringing Sets tribe to see upcoming "visitors from the sky." Refusing, the anthropoids attacked the invaders, exposing them as Serpent Men and driving them from the haven. Immediately afterward, the "visitors from the sky"— the First Host of the Celestials — arrived. Gaea guided the man-apes to the Celestials, who studied them and experimented upon them, genetically diverging mainstream humanity, the Eternals, and the Deviants. The Serpent Men asked a boon of the Celestials but were driven off by Arishem the Judge.
Long before the dawn of humanity, the Serpent Men created the Cobra Crown via power drawn from Set to create "an empire of the Earth" from the land that would become Valusia. The Crown was worn by Serpent Men kings but eventually proved defective and was hidden under a black shrine to Tsathoggua, a toad-demon ally of Set's. It was guarded by a living stone idol of the Toad-God on the Nameless Isle and would not be found for millennia. Set also empowered the lesser-powered Serpent Amulet and other talismans.
Some members of the Elder Race — a seemingly humanoid race predating humanity and composed of numerous wizards—such as Thulsa Doom, as well as certain sects of Deviants, worshiped Set as their god. As Homo sapiens emerged, the Serpent Men enslaved them for an epoch while vying with the Deviants and other empires;demonic races, such as the N'Garai and Undying Ones; or Elderspawn (descendants of the Elder Gods), such as Harpies, Spider People and Wolf Men. Circa 18,500 BC, the Serpent Men were opposed by Valusia's King Kull, who would become one of their greatest-foes, bringing them to the verge of extinction. Kull slaughtered a sect of Set-worshipers and ordered the death of twin infants they had magically created, but they were mercifully spared; the twins, Narcta and Alexus, would achieve vast mystical power before being destroyed 8000 years later.
500 years after Kull's time, when the Deviants had established an advanced empire in Lemuria and conquered much of the Earth, human alchemist Atra sought to overthrow them, allying with Serpent Men to create the Serpent Crown. Set empowered the Serpent Crown and linked it to his mind as a replacement for the Cobra Crown. Atra donned the Crown, but Set then transferred his allegiance to the Deviants, refusing to allow the Crown's power to be used against them. Deviant emperor Phraug, emboldened by their new deity, ordered an attack against the Second Host of Celestials, who had returned for follow-up investigation of the human race. The Celestials shrugged off Phraug's attack and caused a massive nuclear explosion that destroyed the Lemurian continent as well as damaging Atlantis. As a result, the Great Cataclysm devastated the planet, ending this stage of world history. Atra and Emperor Phraug were dead center under the main explosion and died instantly, but the Celestials' power preserved their skeletal remains, left clutching the Serpent Crown as a warning about pride.
Some Serpent Men survived the Great Cataclysm, but later humans took much of the remaining Serpent Men-ruled territory, setting up the kingdom of Stygia in the process, as well as Acheron, circa 15,500 BC. Set was worshiped by the peoples of Stygia and Acheron (as well as Eldoran and other places). Many of the sorcerers there worshiping Set formed the Black Ring coven. Eventually, Acheron was toppled, but Stygia survived. In the succeeding millennia, Set would also be worshiped by Kushites, degenerate cults in mountains between Nemedia and Aquilonia and remnants of Stygian civilization in Shem. Over time Set developed alliances with dark gods, such as Nexxx, as well as fierce enmities with other gods, such as Mitra and the bird-headed Ibis (possibly a manifestation of Thoth);and other demons, such as Xka'Ahk and the spider god Omm. Set also guided the development of his descendent the Midgard Serpent (Jormungand) of Asgardian mythos.
Circa 10,000 BC the mysterious "Dragon of Set" menaced the town Solvantha until being driven off by Cimmerian sorcerer Rham-Skot, who created the Sword of Graven. The Cobra Crown was eventually recovered from the Nameless Isle by the legendary barbarian Conan who destroyed the Tsathoggua idol, but the Crown was later claimed by Thoth-Amon, then leader of the Black Ring. Thoth-Amon attempted to usurp the leadership of Zingara from King Ferdrugo, but another would-be usurper, Villagro, seized the Crown for himself. Villagro's untrained mind caused the Cobra Crown to burn itself out, rendering it useless, and Thoth-Amon fled. Set later seduced the turncoat Mitraic priestess C'harona with promises of power, and C'harona manipulated the people of D'eim to build a tower to Mitra, which was actually a drill used to free rat-like demons serving Set. C'harona became a powerful harpy, but Conan slew her, and the demons perished under the collapsing false tower. Conan opposed and slew many of Set's followers in the Black Ring and elsewhere. Eventually,Conan became king of Aquilonia, and he and his son Conn eradicated the last stronghold of the Serpent Men, though a few others survived.
Following the end of the Hyborian era, circa 8000 BC, Set's worship continued in what was Stygia (which eventually developed into Egypt as further cataclysms reshaped Earth), but an upstart Ennead death god, Seth, adopted serpentine form and impersonated Set, usurping his followers; trapped in his extradimensional realm, Set writhed in vain frustration. Egyptians would later mistake the immortal mutant En Sabah Nur (later Apocalypse) for both Set and Seth.
Set developed new worshipers among the Homo mermanus race, water-breathing humanoids who colonized the now undersea realms of Atlantis and Lemuria 2000 years ago, an Atlantean sect created the Golden Serpent, which magnified the psychic energies of Set's worshipers. Using this they summoned Set but Neptune, the Olympian sea god who served as patron to most Atlanteans, destroyed the sect, though a portion of Set's life force remained with the sects great globe. Neptune set a sea monster to guard the globe over what became known as "Neptune's Wrath." 600 years ago, Lemurian leader Naga had the Serpent Crown retrieved from the skeletons of Phraug and Atra (where it had been found long ago but shunned). Naga embraced the Crown's power and Set worship, and the Lemurians were gradually mutated to have a scaly appearance. Set instructed Naga how to treat the Serpent Crown with material from certain undersea life forms to prolong his life. A group of telepathic Lemurians (later called the Ancients) eventually stole the Crown to end Naga's centuries-long tyrannical reign. They relocated to an Antarctic base containing pre-Catadysmic Atlantean technology left over from the Savage Land's creators and encased the Serpent Crown in metal to dull its seductive emanations. One of the Ancients, Pyscatos, years later gave in to temptation and donned the Crown but ultimately repented, killed himself and destroyed the base in an explosion. Set magically preserved a dynamo of the Ancients, hoping that someday someone would again find the Crown. In 1920, Paul Destine, a crewmate of Leonard McKenzie — Namor the Sub-Mariner's father — aboard the Oracle ship, acquired the metal-encased Crown but fell into suspended animation to adapt to its power. Reviving in 1958, Destine took the name Destiny, calling the Crown the Helmet of Power. Set prodded Destiny into destroying the Atianteans' Antarctic city. Destiny further wiped Namor's memory, leaving him to wander New York City for decades while Destiny returned to hibernation. Destiny re-awakened in recent years and used the "Helmet of Power" to run for the US presidency. Insane with power, however, Destiny removed his Helmet to show he no longer needed it. Ignoring Set's protests, Destiny walked off a tall building's roof and, unable to levitate, fell to his death.