Warning! Spoilers for Heroes Reborn #7 by Marvel Comics below.
Marvel Comics has confirmed that Agent Coulson is working alongside Mephisto and is the person responsible for rewriting reality in the Heroes Reborn universe. In the event's seventh issue, a conversation between Coulson and Mephisto is revealed, where the two conspire to deal with the return of the Avengers in a world where they shouldn't exist to begin with.
Marvel fans most likely know Agent Phil Coulson from his appearances in The Avengers and Agents of SHIELD. However, in the comics, the character has recently gone down a much darker path than his MCU counterpart. Coulson was put in charge of the Squadron Supreme of America in the original Marvel Universe and mysteriously worked alongside Mephisto, who resurrected him after he died. When the main reality was changed in Heroes Reborn, he became President of the United States, while Mephisto is worshipped like a God. Meanwhile, the Squadron Supreme replaced the Avengers.
In Heroes Reborn #7's epilogue by Jason Aaron, Ed McGuinness, Mark Morales, Matthew Wilson, and VC's Cory Petit, President Coulson meets with Vice President Thunderbolt Ross and White House Press Secretary J. Jonah Jameson about the pending threat of the Avengers. Coulson kills both men and tells the press to blame it on sleeper agents from Wakanda. Mephisto (in his demonic dog form) reassures Coulson that he did the right thing by killing them, as any mention of the Avengers could jeopardize their reality. Realizing he can't undo his mistakes, Coulson says he will use the same tactic he employed to remake reality in the first place to make things right: the Pandemonium Cube.
The Pandemonium Cube, otherwise referred to as the Hellahedron, appears similar to Marvel's Cosmic Cube. Do Coulson and Mephisto have an Infinity Stone inside the cube? Also, can the pair rewrite reality again without seriously damaging the timeline they've created? It seems to avoid the Avengers from rallying the world against them and exposing the fraud reality, Coulson and Mephisto are pulling out all of the stops.
With the Squadron Supreme and Avengers fighting one last final battle in the Heroes Reborn universe before the event wraps up, Agent Coulson and Mephisto are feeling the heat when it comes to saving their reality. As their perfect universe starts to collapse on itself and the Avengers slowly seeing the cracks in the Heroes Reborn universe, Agent Coulson and Mephisto are likely going to use the Pandemonium Cube as a last-ditch effort to save everything they created. Even with the Cosmic Cube-like item, Mephisto and Agent Coulson's chances of preserving their reality seem slimmer than ever. Heroes Reborn #7 is in comic book stores now.