While Kang the Conqueror may be the opposite of the heroic Thor, he does have one unusual quality in common with the Avenger's legendary hammer, Mjolnir. This was revealed in Avengers Annual #21, in a story written by Mark Gruenwald with art by Herb Trimpe, Charles Barnett and Brad Vancata.
In this issue, the Avengers and the Fantastic Four team up to investigate claims that Kang has returned to the 20th Century. What they find is a city called Chronopolis, where Kang has merged several different time periods within the limits of a vast city. Kang has also positioned himself in a citadel in the center of the city guarded by many elite commandos. And of course, the Avengers and Fantastic Four fight their way to Kang’s throne for a final battle.
During the story, which is titled 'Kang's World,' the Conqueror reveals to his former love and current enemy Ravonna that he is not motivated by sadistic slaughter but the thrill of the conquest. He states that he comes from a boring time and his only purpose is to escape that boredom. Of course, he goes about it in an immoral way, fighting both heroes and villains just for the sake of the challenge. Kang explains, "I decreed that no conquest I ever undertake be boring, nor shall any person who serves or opposes me be unworthy!" It's an interesting choice of words considering that it's similar to the enchantment on Thor's hammer Mjolnir to dictate who is able to wield it.
While Mjolnir can only be lifted by the worthy, Kang will only battle those who meet the same criteria. In fact, given that the Asgardian definition of worth is partly based on a warrior's willingness to fight on behalf of the Ten Realms, Kang and the hammer agree on some of the same candidates, and both have 'honored' Thor, Venom and Captain America in the past. While Kang's idea of worth may differ form Mjolnir's in terms of motive - the hammer tends to be a force for good - both will only interact with the most significant warriors of all time. In a twisted way, Kang attempting to challenge or recruit an individual is a huge compliment.
Kang actually sees his attacks in this way - in Kurt Busiek, Alan Davis, Kieron Dwyer, Ivan Reis, and Manual Garcia's 'Kang Dynasty' Avengers story arc, the villain describes his war on the team as an honor, enraging Captain America, who is far more concerned with the loss of life that has resulted. Having been created in the early stages of the universe (and likely lasting until its end), Mjolnir takes a similarly long view and actually has its own consciousness, meaning that despite their drastically different presentations, the hammer and Kang are both powerful beings who exist across time, occasionally selecting the most worthy people to receive their attention.
In endeavoring only to engage with those who most deserve his attention, Kang the Conqueror has turned himself into a dark reflection of Mjolnir, always on a mission to seek out the most worthy warriors and crush them under his heel.