WARNING: The following contains spoilers for Justice League: Odyssey #18, by Dan Abnett, Cliff Richards, Rain Beredo and Andworld Design, on sale now.
Avengers: Endgame was one of superhero cinema's most riveting stories, as Earth's Mightiest Heroes had to find the Infinity Stones by jumping through time to rewrite Thanos' snap from Infinity War. This was so they could restore the half of the galaxy the Mad Titan killed, and that temporal mission proved to be very intriguing as the heroes messed with history.
In Justice League Odyssey #18, Jessica Cruz's team is now facing a similar problem, but luckily, they have something more than a Gauntlet or a Time Stone: they actually have a Lord of Time in their ranks. With this person, Epoch, ready and willing, the heroes are now embarking on an Endgame mission of their own to reset the madness in the DC Universe.
The DCU is facing several threats at the moment, with Perpetua rewriting reality thanks to the Apex Predator, Lex Luthor, and his Legion of Doom. Meanwhile, Darkseid has also created his war zone outside time and space known as Sepulkore, and he's getting ready to plan another apocalypse when the new multiverse is reborn. This is why Jessica's faced with a tough task when she meets Epoch, who seems to have everyone's best interests at heart. However, in the past, he's manipulated time for his own gain -- something Orion reminds her of.
In Issue #18, Epoch chats with Blackfire, Dex-Starr and the scientist Arla Hax, as he explains his cosmic lair has stored "implicate time," which means he can reset the established order. In fact, on the device he plans to use, the Revision Mechanism, we see various versions of Epoch strewn across different timelines. These are realities that have come to pass, while others are potential. It's basically him peering into various dimensions the same way Doctor Strange did in Infinity War, where only one solution was possible.
Similarly, Epoch finds there's only one solution in this case: rewriting the past. All these realities depend on this, and for them to have a future, he needs to revise time. However, he needs help, which is why Jessica and Orion are brought into the fold by another version of Jessica. Time overlaps and overflows are occurring inside Epoch's base, and when they all get together, the Lord of Time reveals he has to perform this reset to combat Darkseid, Lex, Perpetua and another mystery player as they'll all crumble reality beyond repair.
With the Justice League also going into a special realm, the latter could be the unknown threat Epoch mentioned as they're off on another Endgame-esque mission of their own. That said, the coalition is wary about chronological tampering, but with Jessica having a mental bond with Cyborg (who's corrupted by Darkseid), she realizes this is the way forward. It seems Vic Stone calculated what needs to be done, and with Epoch able to alter the space-time continuum and fix history, Jessica wants to push forward.
He plans to erase these threats to restore things to before the villains wrecked reality, so we can see his mission has parallels to the Avengers wanting to snap the dead back to life. That was their way of fixing reality, but as with that mission, we don't know who'll return, who'll be erased and just how remodeling the past will affect the present and future. Jessica seems confident enough, however, so let's hope the trust and faith she places in Epoch won't come back to haunt her.