Kang the Conqueror made his first appearance in Avengers #8 (Sept. 1964)
Nathaniel Richards, a scholar born in the 30th century, becomes fascinated with history and discovers the time travel technology created by Victor von Doom. Richards then travels back in time to ancient Egypt c. 2950 B.C., aboard a Sphinx-shaped timeship, to become the Pharaoh Rama-Tut, with intentions of claiming En Sabah Nur—the mutant destined to become Apocalypse—his heir. Though briefly blinded in a crash, a radioactive herb restores his sight after frightening the Egyptians by firing his ray-gun. Richards's rule lasts for a time, until his defeat by time-displaced heroes from the 20th century, the Fantastic Four, who had traveled back in time (with some help from a time-traveling Doctor Strange and Khonshu). The Fantastic Four are placed under mind-control by Rama Tut's Ultra-Diode Ray; he makes Susan his Queen, puts Ben to work on the ship, plants Reed as a lookout for his armies, and makes Johnny Storm his court jester. The four of them escape in the Sphinx, while Tut flees back into time, and an explosive device destroys the Sphinx. He eventually returns to rule in ancient Egypt, and encounters the time-traveling West Coast Avengers.
Embittered by this defeat, he travels forward to the 20th century and meets his ancestor Doctor Doom, adrift in space near Jupiter. He returns him to Earth. They suggest they might be the same being, but at different points in time, so will not attack the Fantastic Four together, as they claim if one is defeated, the other will be unable to exist. Richards then tries to return to the 31st century, but instead finds himself one thousand years further in the future due to an energy failure. This world is inhabited by warring factions that do not understand the technology created by their more advanced ancestors. Kang designs an armor based on Doom's using 40th century technology, and again travels to the 20th century, thus creating an alternate timeline: Earth-689. Calling himself the Scarlet Centurion, he manipulates the Avengers from this timeline — the original team — into apprehending all heroes and villains (following their first encounter with the Space Phantom. The Centurion transports the Avengers from Earth-616 to his timeline, hoping that they will defeat their Earth-689 equivalents, and can then be disposed of. They are able to force the Centurion from this timeline, after which Uatu reveals that he is Kang. He battles the Squadron Supreme on an alternate Earth. The Centurion returns to his home century, and reinvents himself as Kang the Conqueror Using the resources at his disposal he establishes an empire. But this world is dying, and so he decides to take over an earlier, more fertile Earth.
On Kang's first foray into the 20th century where he expects to meet Doctor Doom, he attempts to conquer this time period and meets the superhero team the Avengers, he reveals how he returned and battles them. He traps the Avengers in his ship using a tractor beam, although Wasp and Rick escape. He says the world has 24 hours to surrender to him. The Teen Brigade pretends they want to help Kang, but drop an energy cylinder to delay him after they gain access to his ship. Thor is freed and he then frees the other members. The Wasp gets Giant-Man a weapon that wrecks Kang's battlesuit and his missiles. Kang releases radiation that beings from the year 4000 are immune to, but Thor uses his hammer to absorb the rays and send them back at Kang, which not even his immunity can stand, after which he is forced to escape to another time. Kang is furious and swears vengeance, and battles the Avengers to a stalemate, using a Spider-Man robot while Iron Man is briefly away from the Avengers, in a Temple with a nerve gas to weaken them after the robot lures them there by claiming the Masters of Evil have kidnapped Iron Man and taken him to the temple, but the real Spider-Man had found out about the robot with his spider-sense and destroys the robot after deactivating it during an aerial battle. The Avengers realize Kang was behind this.
Kang returns, attempting to win the hand of Princess Ravonna of a puppet kingdom, by demonstrating his power to her father by battling the Avengers, who he kidnaps using a time machine he disguises as part of their mansion. The Scarlet Witch uses her power to break out of giant jars they are imprisoned in. She pulls a lever to free the others. However they are paralyzed by a device of Kang, though Quicksilver evades it with his speed. Captain America reveals himself to Kang outside the Mansion, so is sent to the future. The Avengers reform and attack Kang, who gives a signal to his army. His men attack the kingdom and finally get to the Avengers, who are defeated. Later after one of his commanders (Baltog) rebels he frees the Avengers to fight with him. They get the support of a group of citizens and break into the armory. The rebellion succeeds, and Baltog is captured by Quicksilver. Kang then transports the Avengers back to their own time. However, Ravonna is mortally wounded by Baltrog, when she leaps in front of the blast meant for Kang, realizing she loved him. Baltrog is then executed, while Kang laments Ravonna. Kang was unable to revive her, so kept her body in stasis.
Later he came from the 25th century and after defeating and imprisoning Merlin he attempted to take over King Arthur's Court and change history by attacking the rest of the world. He defeated King Arthur and many of his knights, sending them into exile. But Uatu the Watcher sent the Human Torch and Thing back in time. They battled his army and the Torch released Merlin. After his army was turned against him by Merlin, Kang was forced to flee. The Watcher then sent the two heroes back to their own time. In an encounter with the Thunder God Thor while utilizing his Growing Man to test it, Kang's disguised time travel vehicle is destroyed by Mjolnir as he attempts to get back to his own time period. Kang returns and enters into a wager with the cosmic entity Grandmaster in hopes of restoring life to Ravonna, and uses the Avengers as his pawns against the Grandmaster's newly created champions, the Squadron Sinister. This also ends in a stalemate thanks to the intervention of the Black Knight; in a second round, the Grandmaster transferred three Avengers - the Vision, the Black Panther and Yellowjacket - to Paris in 1941. The Grandmaster then summoned the Sub-Mariner, Captain America and the android Human Torch from that period as his unwitting pawns to battle the Avengers. When the Avengers won the battle, the Grandmaster returned the Torch, Sub-Mariner and Captain America to where they had been and returned the Avengers to Kang's citadel. Since Kang won only one round of the game, he did not win the power of life and death - to save Ravonna and defeat the Avengers. He had to choose one or the other, so he requested the power of death to kill the Avengers. Since the Black Knight was not a member of the Avengers, he was not killed and was able to defeat Kang. The Grandmaster removed the power of death and revived the Avengers. Kang later has a brief encounter with the Hulk, who he utilizes in a scheme to change Earth during World War I, as he is unable to enter 1917 due to a time-storm. Kang attempts to trick the Hulk into killing his own ancestor by stopping the Phantom Eagle destroying a cannon that was about to attack the Allies—and thus potentially negate the formation of the Avengers. The Hulk stops the Eagle, but accidentally destroys the cannon himself, and when Kang tries to keep the Hulk in 1917, he is hurled into the 'limbo between the millennium'. Later he tried to invade the 23rd Century, time period of Zarrko, and tries to capture the Avengers once more. Spider-Man and Iron Man are taken forward by Zarrko so he can get into Kang's facility. Zarrko then sends back three devices which will reverse the natural state of humanity all over the World except for an American nuclear base, making it easy for him to steal weapons from there, with which he can defeat Kang and rule his time. This scheme is foiled by Spider-Man and the Human Torch. With the help of the Inhumans, Spider-Man returns to the 23rd Century and defeats the two villains.
Several months later Kang reappears, seeking the Celestial Madonna for a mate, whom he believes is on Earth. The discovery that it is the Avenger Mantis leads to another confrontation with the Avengers. The Avengers are aided by a futuristic version of Rama-Tut, who had returned to ancient Egypt in his old age and ruled for ten years, and then placed himself in suspended animation to revive in the 20th Century. This Rama-Tut has abandoned his identity as Kang and seeks to counsel and change his younger, conquering self. While Kang is foiled in his quest for the Celestial Madonna, Rama-Tut is unable to prevent the accidental death of the Avenger the Swordsman. As Kang escapes, the Avenger Hawkeye chooses to pursue him (courtesy of Doom's time-travel machine), which results in a final battle in the Old West in 1871. Aided by the futuristic Rama-Tut once more—who has evolved after a journey to Limbo and a study of time into Immortus —Hawkeye, Thor, and ally Moondragon confront Kang, with the help of the Two-Gun Kid. In trying to defeat Thor, Kang draws on an excessive amount of energy and destroys himself.