In a way, Thor was Marvel's reaction to Superman, a very powerful folk hero with a civilian secret identity that was in love with his co-worker. The physician Donald Blake was a handicapped man that transformed into a mythic hero by tapping his stick, but aside from a vague mythology connection, his stories had little to differentiate them from many of his costume compatriots. Early on, the creators settled on his evil half-brother Loki being his chief foil, with their rivalry overseen by the leader of the pantheon, Odin.
Jack Kirby never stops tinkering with the latter's design, with the All-father changing appearance in every issue. Much more tellingly, the creators slowly step away from Donald Blake as a human host for Thor, and start treating them as one and the same. Much like the murky origin, the character is slow to pick up a gallery of foes, with the creators resorting to uninspired Silver Age cliches (a double, an evil wizard), with an early low point being a retooling of the Fantastic Four's first encounter with the Skrulls. Some of these characters, such as the Radioactive man and Lava man would later work their way into other comics, but by and large the comic was hurting from not receiving Lee and Kirby's full attention.
In these early days, Lee and Kirby are slow to make full use of the Norse mythology that first inspired them and Thor is basically used as simply a powerful Silver Age superhero, frequently foiled by the Mister Hyde and Human Cobra teaming up. Beginning with "Journey into Mystery" #97, the character was additionally featured in a supplement called "Tales of Asgard", that started by retelling original Norse myths in pages consisting of four panels, which really brought Jack Kirby's contributions to the fore.
In the main feature, Thor continued to fight with the likes of Grey Gargoyle, with the subplots basically relegated to the budding romance between his civilian alter ego and nurse Jane Foster, who was unlikely to win Odin's favor. Thor was also a founding Avengers, with the team-up title serving to introduce him to the company's wider readership. Following the obligatory crossovers with the X-Men and the Hulk, the title finally gets around to introducing an iconic Silver Age villain in the Absorbing man, made into a credible foil thanks to his ability to transform into the materials he touched.
After finally deciding to dig into Thor and make the title work, Lee and Kirby launch into a longer saga pitting Loki against Thor, in the process introducing the Destroyer armor. Sporting a strong Kirby design, the Destroyer was to remain a staple of Thor mythos, but Loki was proving much more problematic. Despite receiving constant attention, Thor's evil sibling seemed slow to develop into an interesting foil, and was basically relegated to a role of laughing maniac, a petty wizard who enjoyed being evil and dreaming of seizing his father's throne.
The back-up "Tales of Asgard" continued to reintroduce the heroes of Norse mythology, such as Balder the Brave and Heimdall, the guardian of Asgard's rainbow bridge. These characters were slow to reappear in the main Thor stories, which were still benefiting from the increased focus. In Lee and Kirby's hands, Hercules, the Greco-Roman demigod served as a perfect foil for their protagonist, with the hedonist champion standing in stark contrast to the dignified Thor. The heroes were quick to establish a friendly rivalry, with Thor's loyalty to his opposite number in the different pantheon a driving force behind the character's another memorable early adventure.
In every way that matters, Lee and Kirby were finally hitting their stride, which meant further changes for Thor. Specifically, the creators continued to step away from his civilian life, with doctor Donald Blake's practice getting increasingly sidelined for the epic adventures. As the creators were opening up the outer space to add another dimension to their hero's adventures, Jane's continued to act as Thor's human anchor, with the hero that once labored over revealing his human identity to her now considering whether their marriage would gain his father's approval.
Thor's outer space adventure introduced the memorable characters of Rigellian Recorder, Ego the Living Planet and the High Evolutionary, once again proving how far the creative team's come from the title's meager beginnings. Stan Lee and Jack Kirby were really hitting their stride with "Thor", featuring memorable characters and settings each issue, that have remained the staples of the characters ever since. Yet even then, the duo had to slow down for an issue, to resolve the question of Jane Foster. Thus, #136 pitted Jane against Odin's scorn for his son's mortal paramour, at the same time introducing Lady Sif as the character's new love interest (a different version of Sif was introduced as Balder's sister in an early "Tales of Asgard" back issue).
Lee and Kirby were not at all subtle in giving Thor a female companion that could carry her own in battle, making her a much more natural part of the title. Another multipart story introduced Ulik the Troll, before settling down for a series of more pedestrian issues. Thus, our hero faces the Avengers' arch-foe Kang and his android, with another robot to follow in the very next issue's episode. There is a momentum that propels all of these stories, even when they are as inessential as a fight with Fantastic Four's Superskrull.
A fight against the Enchanters (no relation to Enchantress, introduced in an early Lee/Kirby issue) quickly turns deadly and raises the stakes for the title's increasingly grandiose stories. Thor's Asgardian allies finally start playing a larger role in the main plot, even as the back-up that introduced them was discontinued with #145. The complicated relationship between Odin and Thor begats an oddball story of a powerless Thor working for the Circus of Crime, but at this point there is such a rhythm and energy to the title that the reader is liable to find charm in the creative duo's indulging their whims.
Having made Loki into Thor's arch-villain, Lee and Kirby naturally return to the character, who serves to introduce another of Marvel's perennial Silver age supervillains - the Wrecker. His debut signals the beginning of another multipart epic, benefiting from having a workable cast of characters. Hela, the Norse goddess of death makes a memorable early appearance as Thor battles life and death to help his friends. At this point, the title is making the most of its potential as a vehicle of retelling heroic legends by using Marvel's Silver Age superhero formula, and the reader is delighted to be along for the ride.
It's interesting to ponder Thor's companion Balder the brave's place in Lee and Kirby's work. Whereas Thor as depicted in these pages still seems torn between Earth and Asgard, his Asgardian friend is continually depicted as extremely competent and fiercely loyal. After envying Thor for having Sif at his side, the creators provide the supporting character with his own paramour, in the guise of beautiful Karnilla. By making her into a witch queen, the creators make for an interesting contrast and add more drama and flavor to their ever expanding cast.
With the same care applied to the main plot, Thor once again encounters Ulik, with the Troll reawakening the ancient evil that is Mangog. Despite the unfortunate design, the villain's appearance signals probably the strongest Thor story to date. With the monster powered by the anger of an entire race seemingly wronged by Odin, the powerhouse makes its way across Asgard to the Odin's throne, intent on unleashing Ragnarok against the Nordic pantheon.
Thor's "Tales of Asgard" companions make their first real appearance in the main title and are dully dispatched by the unstoppable evil of Mangog, in his attempt to raise the Odinsword against all that our hero holds dear. Following what is without a doubt the creative peak of the Lee and Kirby run, the duo stops to provide a recap for their previous work with the character, in the process making another set of revisions to his meager origins. Namely, #159 tackles the question of Donald Blake's relationship to the Norse deity that he inhibits, in effect providing a new origin for the popular character.
At this point, it's unavoidable to discuss the impending split between Lee and Kirby, as the period corresponds to the time the artist has been said to have saved his new characters and concepts to be used by his work outside of Marvel. Perhaps this explains the amount of space given to the concepts the pair have already established in their previous work, but it also speaks to a larger question, that of the authorship of the stories themselves.
Jack Kirby, unsatisfied with the compensation for his work that won the hearts and minds of Marvel fans felt that he was contributing much more than the artwork on the company's magazines. The writer/artist felt that he was largely responsible for creating the stories themselves, working from a very loose plots devised with Lee. 1970's Jack Kirby was no longer an inventive artist tasked with helping birth Marvel's Silver Age superhero line - he was a superstar and a major draw for the company that has richly capitalized on his work.
By this point, he was very aware of his strengths as a storyteller, and his last issues on "Thor" are certainly seem like the work of a man who is holding back on unleashing the full brunt of his talent. Seeing Thor fight another robot in Thermal man and watching his rematch with the Wrecker seem inconsequential even compared to the prolonged fight against Galactus that returned the title to outer space and reunited Thor with the Recorder. Ironically, a one-off story featuring Thor trusting to a science fiction procedure to save his former love Jane Foster reads like a classic Jack Kirby tale.
Ulik's reappearance tied to another bout with the Circus of Crime is merely uninspired, while the next issue's encounter with Crypto-Man goes so far to rework an entire earlier issue of "Thor". It is no wonder that Kirby was gone before the end of the next storyline, itself largely a callback to the earlier Mangog conflict. Loki and Surtur make much less of an impression with their plan to attack Asgard, and by the time the reader notices that Jack Kirby is missing, they will be given little reason to continue.
What awaited was a short run with Lee scripting over John Buscema's pencils, mostly notable for introducing the legendary penciler to the title that he'll be working on for years on end. Unfortunately, starting with the story featuring the Stranger, Buscema's work on the title will provide full of stories that can largely be categorized as harmless diversions that kept the character on the newstands, in lieu of producing entertaining work that could compare to the Lee/Kirby original.
Some of Kirby's last "Thor" pages end up providing an introduction to an instantly forgettable story of Loki trading places with Thor. One Silver Age cliche is supplanted by another as Thor fight Doctor Doom, another staple of Fantastic Four franchise that has had such an unexpected impact on the title. Lee sticks around for a mystical adventure pitting Thor against the all encompassing other-dimensional evil of Infinity, that provides a strangely ominous atmosphere and highlights Buscema's strengths as a penciler. Hela once more plays a larger ruler in the story, before Lee returns to Loki.
Lee will return to his co-creation a couple of times, but never in an ongoing commitment. After experiencing the pinnacle of his writer/artist career with the Fourth World books as DC, Jack Kirby eventually returned to Marvel in 1977. His latter day work on "the Eternals" proved surprisingly influential on the Buscema drawn Thor plots, but it was his entire body of work that has inspired and continues to inspire countless writers and artists working in the superhero tradition.