Updated: Jul 9, 2019
This story came out 2018 and by the time the site had been published it had been a month since it had come out and at the time there was a lot going on and I ran out of time. This is a way for the site to recap it. The first issue begins with every green lantern being called to the source wall, the walls of reality. It turns out that the Justice League had put a crack in it after they fought back the dark multiverse in dark knights metal. Guy Gardener literally explained that the old rule book just went up in flames.
This is when we cut to earth and we see that Brainiac has just defeated the earth's heroes to prove a point that they're not ready for they've unleashed. They all wake up and discover that they're all in different costumes and that they've all been separated into teams with matching uniforms. They're not even paired with their ideal teams as some heroes have been allied with some of their villains.
Robin (Damian Wayne) decides to try figuring out what is going on and he bumps into Brainiac who promptly informs Robin that today they were allies. This is enforced by the fact that the Justice League are with him and Brainiac has Wonder Woman's lasso wrapped around his arm.
Brainiac goes on to explain that when the source wall was cracked it released beings known as the omega titans that have existed since time began. They represent the four fundamental forces of life: Mystery, Entropy, Wisdom and Wonder. The titans seek to devour the worlds that have grown to represent each of their forces. So if a planet's divine nature was entropy then the titan of entropy would devour that world. To do this they planted seeds of energy that represents each of Omega titans representations on each planet and the one tree that grew the tallest would mark which Omega titan got to devour the planet. Brainiac brought them all hear because the Omega Titans had arrived on his home planet of Kallu and they've all been brought here to stop them consuming his planet along with every other. Unfortunately, he thought it was a good idea to bring in more than heroes...
Literally as this happens Amanda Waller of all people has captured the strongest psychics in the world so she can hack Brainiac and have an understanding of what is going on. By doing this she ends up frying him.
This leaves the Justice League stranded on Kallu with no idea what to do or how to do it. All they can do is try to fight back against the omega titans that each team was assigned to battle. They also need to stop the seeds that the Titans planted from growing.
At this time Team Entropy meets Brainiac 2.0 while Green Arrow and Amanda Waller discover that Brainiac planted one of the Omega Titan seeds on Earth so they'd devour it if the Justice League failed.
Believe it or not they fail. Kallu is destroyed but luckily a planet wide evacuation was already in progress so it was far from inhabited. Starro attempted to take control of one of the Omega Titans but was instead torn apart as he's the equivalent of a moth compared to the Titans.
To make matters worse the omega titans not only see people like Doctor Fate and Superman like flees to be swatted away and they're now on earth getting ready to devour it. They attempt to get Brainiac 2.0 to assist them but he refuses. He believes that this is technically the Justice League's fault and that they deserve every bit of pain and remorse they're going to get. So things aren't going too well.
Then Brainiac 2.0 uses the teleport to earth so he can actually speed up the growth of the cosmic seed there. That's when the Green Lanterns show up on Earth and are ready to assist the Justice League with their new plan.
They're going to use the combined energies from each team to create a new seed that they can launch at one of the Omega Titans so the others devour it. It's crazy and it just might work.
TIt actually works and Green Arrow fires it into the Titan of Entropy and the others proceed to tea into Entropy and they're satisfied with their meal. This leaves the universe without it's primordial representation of Entropy which will become an issue later.
This is when the narration explains that the Omega Titans are just the beginning. Everything that was trapped behind the source wall was trapped there for a purpose by the source and now the prison wall has a crack. Every bad thing that was ever trapped behind it now has an outlet to escape. The Justice League has now recognized this and they need to create new teams to cope with the new threats that have arisen such as the upside down man and the Ghost sector. They will need two teams such as the New Justice League Dark and Justice League Odyssey.