Warning! Spoilers ahead for Heroes Return #1
In the finale for Marvel Comics' Heroes Reborn, it's been revealed that the latest reality-changing event was merely an audition for a much darker threat on the horizon for the Avengers. Thanks to a hellish version of the Cosmic Cube wielded by President Coulson, the corrupted former agent of SHIELD warped the world, manipulating it at his will, making the Earth's Mightiest Heroes the Squadron Supreme of America while making sure that the Avengers never assembled. However, the event's conclusion with Heroes Return revealed that it was only a prelude, a means to an end for Coulson's master Mephisto to prove his worth.
In prior issues of Heroes Reborn, it was revealed that there was a handful of Avengers who actually remembered the world as it was meant to be, including Blade and Maya Lopez's Phoenix. Eventually, a version of the Avengers reassembled despite Coulson's best efforts, and an epic battle was held in the culminating Heroes Return #1 from Jason Aaron and Ed McGuinness between the Avengers and the Justice League analog that is the SSA. While the evil president entered the fray himself with his Pandemonium Cube, he was still defeated. Not only that, but the combined power of the Phoenix and Starbrand against the cube was enough to restore the world back to how it's meant to be.
While one would think that Mephisto would be disappointed by the loss, the issue's end actually sees him totally fine, speaking to a mysterious group and revealing that the entirety of Heroes Reborn was simply a test and display of his individual power. He proved himself able to warp reality so much that he was able to fashion a world were Mephisto himself was worshipped a god, rather than the devil he truly is. He asks his audience to imagine what could be done with more Mephistos working together, and it's revealed that he's speaking to The Council of Red, a conglomeration of Mephistos from across the Multiverse, which can't be good for the Marvel Universe in the near future.
While Coulson was summarily dealt with and imprisoned in the Cosmic Cube itself, it seems as though Mephisto only saw the world his minion envisioned as a glorified audition. He didn't care if there was success or failure so long as it provided him with the ability to effectively try out for and make his case for a spot on the council, getting their attention, respect, and help in conquering the Earth.
As a result, one can imagine that an army of multiversal Mephistos is going to be pretty challenging for the Avengers down the line, and it will no doubt be greater and darker than anything they had to face in this recently altered reality created by the dark President Coulson. Heres's hoping the real Earth's Mightiest Heroes are up to the challenge in future issues of Jason Aaron's Avengers now that Heroes Reborn has concluded.