Spoilers ahead for Avengers 1,000,000 BC #1
In Marvel Comics' new one-shot starring the Avengers of 1,000,000 BC, the history of the true first Black Panther has been revealed in full, effectively rewriting the history of the original. Comprised of Earth's first heroes to wield the primordial powers, the Ancient Avengers began a legacy of protecting the world that would continue for countless generations all the way to the present. However, the first Black Panther was also the first Avenger to give his life in the name of keeping the world safe.
A creation of Jason Aaron, the Ancient Avengers of 1,000,000 BC have had appearances throughout Marvel's ongoing Avengers series from Aaron and artist Javier Garrón. Currently, the present-day Avengers are traveling back in time to save their ancestors from annihilation at the hands of the demon lord Mephisto and his Council of Red, a legion of his variants who've agreed to help him end Earth-616 and its surplus of heroes. However, this new one-shot from Jason Aaron and Kev Walker reveals when this original team of Avengers disbanded thanks to Odin, the Phoenix Force, and the birth of Thor.
While the primary reason the Avengers went their separate ways was due to Odin trying to marry the Phoenix with a surprise wedding (and then getting rejected), the team tensions truly began with the death of the first Black Panther following their battle against the Frost Giant Laufey and Hyve from the Negative Zone. While giving her condolences, the Black Panther's true name was revealed to the Phoenix by his tribe. However, it turns out that this first Black Panther was not Bashenga, the recorded and known Black Panther who was said to be Wakanda's first protector.
As revealed by the rest of the issue, the Black Panther tribe took Mosi's body back to their mountain of vibranium and closed their doors, removing themselves from the world in response to the death of their greatest warrior. As such, it seems as though Bashenga would become the next Black Panther many years after Mosi's death, beginning the true line of succession as Wakanda's protector and king. While it does rewrite the history of the Black Panther mantle, it's certainly not the most egregious retcon the Marvel Universe has ever seen (especially with it allowing a Black Panther to be part of the prehistoric Avengers).
While Mosi was the first protector of the Black Panther tribe, perhaps Bashenga is considered to be the first Black Panther of the kingdom of Wakanda after their society had advanced enough to build their own nation and borders. At any rate, it's certainly a notable rewrite of the Black Panther's overall history. Avengers 1,000,000 BC #1 is on sale now.