Last issue six Avengers learned the history of Immortus from a Space Phantom, before being betrayed to Immortus by their 7th member Yellowjacket. Meanwhile Rick Jones had taken off on his own. This issue is mostly taken up with Kang reviewing his own history, until Rick and the Kree Supreme Intelligence return.
Last we saw of Kang in #3 he was in Chronopolis as Immortus collapsed it to make the Forever Crystal. We now find he escaped that fate and retreated to another stronghold in Purgatory.
Kang was born into a highly-civilised 30th Century on an alternate Earth. This Earth had been rebuilt after a nuclear war by Reed Richards's father Nathaniel. Kang's genealogy is muddled, but he may be descended from Nathaniel Richards, or possibly from Dr Doom, or both. Seeking adventure he found his ancestor's time machine, rebuilt it as a Sphinx and went back to Ancient Egypt to rule as Rama Tut.
In Fantastic Four #19 the Fantastic Four used Dr Doom's time machine to visit Rama Tut, and forced him to flee in the chronosphere heart of the Sphinx. En route to the future Rama Tut rescued Dr Doom from space in FF Annual #2. Rama Tut believed Doom to be his ancestor, but they also speculated confusingly that they might be the same person separated by time travel.
After leaving Dr Doom, Rama Tut was thrown back in time a bit to the end of Avengers Annual #2. There he appeared to the Avengers as Scarlet Centurion, causing a divergent timeline. He pretended to be an ally of Avengers but led them astray. He kept the original Avengers lineup, stopping Hulk from leaving and preventing the revival of Captain America. He persuaded them that the future of humanity depended on them imprisoning all other superheroes and supervillains. The current Avengers accidentally arrived in this divergent timeline in Avengers Annual #2 after returning from WWII in Avengers #56. They realised that Centurion had created a dictatorship, and used Dr Doom's time machine to cast him out of the alternate timeline.
Resuming his journey to the future Rama Tut overshot his own 30th Century and ended up in the war-torn 40th Century. He speculates that Immortus may have caused the overshoot. Here he took the name and armour of Kang and began his career of conquest. He conquered Earth, and then alien races such as the Badoon.
Tired of ruling a devastated Earth, Kang returned to conquer the 20th Century in Avengers #8, and attacked Avengers with a Spider-Man robot in Avengers #11. He continued to monitor Avengers, e.g. at their line-up change in Avengers #16.
Kang continued to expand his empire in the 40th century, conquering other space empires such as the Matriarch's Universal Church of Truth, and other-dimensional empires such as the Courts of Kosmos, whose size-changing technology he used to create his Growing Men Stimuloids.
Kang's empire was too large to personally control in detail. He had many subservient rulers under him. One such was King Carelius, whose daughter Ravonna Kang loved. But Ravonna didn't love him, and Carelius wouldn't marry her off to him. In Avengers #23-24 Kang brought the Avengers to the 40th Century to demonstrate his might to Ravonna. He demanded Ravonna in marriage. But his right-hand man Baltag demanded Carelius and Ravonna be executed as rebels. Baltag thought Kang had grown weak, and led a rebellion. Kang and Avengers successfully defended Carelius's castle, but Baltag tried to shoot Kang. Ravonna realised she did love him, and took the blast instead. Kang returned Avengers to 20th century, and put Ravonna in suspended animation pending a cure.
Kang threw himself back into his conquests, including the 40th Century Shi'ar Imperium. Then he took a fateful trip back to the 20th Century in Thor #140 to retrieve a Growing Man that had been accidentally activated. Thor used his hammer to send Kang to Limbo. Here he found a seemingly-dead Immortus, and used his technology to snatch Ravonna from just before her death, only to discover that this resulted in a divergent timeline where he died instead of her.
This lead him to further discover that his frequent time-travelling had spawned multiple alternate-reality copies of himself. Up to now Kang's tale has taken a leisurely pace. Understandably less space is devoted to the alternate-reality adventures, even including several stories in one panel. But sometimes these quick flashes hide multi-issue epics, or stories of some importance to Kang's future. Those depicted are:-
The builder of Chronopolis, as seen in a flashback in the Terminatrix backup story in Avengers Annual #21. Thus the Kang who was besieged in Chronopolis in #3 was not the one who built it.
A Kang who went back to Camelot in the Human Torch & Thing story in Strange Tales #134 to change history so that Avengers and Fantastic Four won't exist. Watcher sends Torch & Thing to stop him. This Kang doesn't yet know that changing the past won't change the present.