Marvel Comics. However, for decades Mjolnir had a caveat that not only made it one of his strongest weapons but also turned it into one of his greatest weaknesses, as if he lost it for more than 60 seconds, he would revert back to his mortal form of Donald Blake.
Thor Odinson first appeared in Journey Into Mystery #83 by Stan Lee, Jack Kirby, and Larry Lieber. Based on the god from Norse Mythology, Thor quickly became one of Marvel's most iconic heroes as he would star in his own epic solo adventures and also became an original member of the Avengers. One of Thor's powers that has largely been left in the past is his need for a human host - an idea that also meant if the God of Thunder was without his hammer Mjolnir, he would revert into his mortal being.
In Thor's earlier stories, it's established that Odin's enchantment on Mjolnir also included the rule that if Thor abandons his hammer for more than 60 seconds, he would turn into Donald Blake. In order to turn back into Thor, Blake would need to hit his cane against the ground. The rule created some real difficulties for Thor, as if he was separated from his hammer for more than a minute, he would lose his strength and powers entirely. So, all a villain had to do to strip him of his powers was separate him from Mjolnir and Thor would change from god into a weak human.
While Thor's hammer always almost finds his way back to him, the 60-second rule presented a number of challenges for writers. Thor literally couldn't be split from his hammer for a prolonged period of time, otherwise, he would lose all of his powers. Over time, the rule (as well as Thor's need for a human host) has been downplayed and largely abandoned.
Despite Thor losing the 60-second rule, it would continue to live on in Marvel Comics in a different way. In Walter Simonson's iconic run on the character, long outlasted its purpose with Thor. With Beta Ray Bill, the enchantment allowed him to revert back to his original identity without the constraints of time.
The power definitely worked better for Beta Ray Bill than it did for Thor, as he could transform back to his Korbinite form whenever he wanted to. The enchantment never fully made sense with Thor as it made one of his greatest strengths his biggest weakness. Thankfully, Marvel abandoned the concept and let Thor continue as his own full-fledged hero.
