Everything starts out with a mysterious figure known as Pariah. He is the witness of universe after universe being destroyed. He sees the universe of Earth-3 disappear. Even the Criminal Syndicate and Alexander Luthor Sr. are unable to stop its destruction. Alexander Luther Sr. and his wife Lois know that they can not stop the destruction of their universe so they send their son Alexander Luthor Jr. to another dimension in hopes of saving his life. The pod with Luther Jr. goes to the universe of Earth-3. In an obvious parallel to the Superman origin.
Lyla and the Monitor also watch as universe after universe is destroyed. In an attempt to stop the end of existence the Monitor sends Lyla as the Harbinger to find the one the Monitor has selected to save it. Harbinger separates into multiple selves and takes off to multiple universes and times. She summons King Solovar from Earth-1's Gorilla City, Dawnstar from Earth-1's future, the first Superhero known as Firebrand from Earth-2's past in WW II, and the Azure Avenger Blue Beetle from Earth-4. One of her forms is sent to find Arion but her body is taken over by one of the shadows of the Anti-Monitor. Another Harbinger summons Psycho-Pirate from Earth-2.
The possessed Harbinger finds Arion from Earth-1's distant past and after toying with him she summons him as well. Meanwhile Another Harbinger summons Firestorm and Killer Frost from Earth-1. Harbinger gets Psycho-Pirate to make Killer Frost fall in love with Firestorm. The Monitor watches all of this. One by one superheroes and villains are called to the Monitor satellite. Others include the Golden Age Superman of Earth-2, Obsidian of Earth-2, Cyborg, Geo-Force, Green Lantern: John Stewart, Dr. Polaris and Psimon all from Earth-1.
While on the satellite the confused group are attacked by Anti-Monitor Shadows. They are dispatched fairly quickly. After a battle, the Monitor shows up and helps them defeat the shadows.