Divergent Series - Event: Metal
The last two major events from the DC Comics New 52/Rebirth era that have analogs in the DC Heroes Rebirth campaign timeline are Dark Nights: Metal and Event Leviathan. Both events retain their major elements, though the details vary based on the needs to fit the DC Heroes Rebirth continuity.
The remaining major events from the comics in the Rebirth and post-Rebirth era have no place in the DC Heroes Rebirth timeline. The Flashpoint-induced New 52 reboot never happens in the DC Heroes Rebirth world, which negates several later events. With no trauma of being removed from history and his marriage and children erased, Wally West will not be sent to the Sanctuary and so the events of Heroes in Crisis do not happen (this does not preclude the existence of Sanctuary or a similar facility in the DC Heroes Rebirth universe). Similarly, the Watchmen's Doctor Manhattan was never a part of the timeline, there was no New 52 reboot for him to be revealed as the cause of and therefore no Doomsday Clock event. Finally, though a version of Dark Nights: Metal does happen in the DC Heroes Rebirth timeline, the larger DCU cosmology that surrounds it (Perpetua, the Totality, the Hands, etc.) is not part of the campaign universe. As such the events of Death Metal, Infinite Frontier, and Dark Crisis do not happen.
By the point in the timeline that the new DC Heroes Rebirth campaigns start, the setting has diverged sufficiently from the published DC Comics continuity that any future comic events will likely not occur in the game without significant changes to the story.
Event: Metal
Rather than a detailed rundown of these two events, there will be an overall summary and a description of the details that diverge significantly enough to warrant coverage.
Dark Nights: Metal
The Metal event involves the discovery of the Dark Multiverse, the home of nightmarish worlds that represent the darkest fears of the Multiverse. The Dark Multiverse is also the location of the World Forge, where new worlds are born. The Parliament of Owls, secret worshippers of the demonic Barbatos sought to summon the being from the Dark Multiverse. They used Batman as a pawn, tricking him into becoming the doorway that allowed Barbatos' Dark Knights, nightmare versions of Batman from the Dark Multiverse, and the being itself to cross over. Batman remained imprisoned in the Dark Multiverse, and was used again to lure Superman into a trap. Superman was then used as a power source to drag the Earth into the Dark Multiverse, which would trigger the destruction of the regular Multiverse. Batman and Superman escape and are joined by Wonder Woman, and together the three access the Tenth Element, aka Element X, of the World Forge. They use this to empower the rest of the Justice League and the team are able to defeat the Dark Knights, drive Barbatos back to the Dark Multiverse, and pull the Earth free. They then use the power of the Tenth Element to undo the damage to the Earth and the rest of the Multiverse.
Divergences
There are several key aspects of the Dark Nights: Metal story in the DC Heroes Rebirth campaign that differ greatly from the details in the original.
Justice League
Cyborg is not a member of the main Justice League team in the DC Heroes Rebirth continutity. His place in the story is taken by Steel.
The Hawks
The history of Carter Hall and Kendra Saunders is very different from the published story. In the DC Heroes Rebirth version, Carter Hall's quest is not an ancient one dating far back but a recent one. Their story does not begin with the Bat Tribe and the Bird Tribe fighting at the dawn of history, it begins in Ancient Egypt as it always does.
Carter Hall's journal is still a factor, it is only his quest that has changed. Here his investigations into the Nth Metal are a desperate means of seeking a way to reunite with his beloved Shiera, who seemingly died permanently at the end of Brightest Day. His quest leads him to be captured by Barbatos and chained in the World Forge.
Kendra Saunders, Hawkgirl, died in Blackest Night, and at that point was no longer possessed by the soul of Shiera. In the campaign universe, Kendra is returned to life by the Egyptian god Horus specifically to try and stop the rise of Barbatos. She hides her return from her former allies, joining the covert Blackhawks organization in order to facilitate her new mission. In this case, the Justice League members do recognize her when she reveals herself, but otherwise most of the story events play out similarly.
Perhaps the largest divergence occurs at the end, when Kendra and Wonder Woman have reached the World Forge and Kendra is trying to get Carter to break free from Barbatos' control. In this case Carter does regain his identity, but is not willing to return, seeking instead to move on to the next plane to try and reunite with Shayera. He does, however, bring back a Hawkman, one whose story was cut off. Using the power of the World Forge, Carter brings back Katar Hol, the Thanagarian hero who had been transformed into a strange amalgam of Hawkmen during Zero Hour and whose exile to Limbo had paved the way for Carter's own rebirth. Katar Hol is restored and once again assumes the Hawkman mantle after helping the Justice League defeat Barbatos. Similarly, after the Metal event Kendra resumes her Hawkgirl identity.
Two Tribes
As noted in the divergences involving the Hawks above, their story is not retconned into going back to the dawn of time. In this case the involvement of Barbatos with Batman begins when Bruce Wayne was sent back to prehistoric times by Darkseid at the end of Final Crisis. THeir may still have been warfare between ancient tribes that Barbatos was involved with, but Hawkman, Hawkgirl, and Hath-Set are not a part of it.
Event Leviathan
Leviathan was a global terrorist organization previously controlled by Talia al Ghul. Control was usurped by Mark Shaw, the former Manhunter, who then turned Leviathan towards a new goal. After radicalizing members of several intelligence organizations, Shaw's Leviathan launches several strikes and effectively cripples the global intelligence community in a day. Organizations like Task Force X, Checkmate, ARGUS, Spyral, the D.E.O. as well as groups like Kobra are rendered ineffective or completely destroyed. Leviathan plans to release the deepest secrets of the world's governments as a means to create world peace. The plan is thwarted by a couple of groups of detectives who ultimately uncover Shaw's identity as the new head of Leviathan and locate Leviathan's base. In the aftermath a new Checkmate is created and it is able to thwart another Leviathan plot, after which Talia al Ghul retakes control of Leviathan and Mark Shaw is killed.
Divergences
The primary differences between the Event Leviathan story in the DC Heroes Rebirth campaign setting and the original story are which characters are involved.
The Detectives
In the DC Heroes Rebirth timeline, Barbara Gordon still primarily acts as Oracle and has not reclaimed the Batgirl identity. Batgirl's place in the story is taken by the Huntress (Helena Bertinelli). There is also only one Question, Rene Montoya, and in the campaign version of the event she is on Batman's team of detectives, not Zatanna's. The other difference in Zatanna's team is the presence of Elongated Man; in the DC Heroes Rebirth timeline he is still dead. Instead he and his wife, Sue, are part of Zatanna's team as the Ghost Detectives. The newest Manhunter, Kate Spencer, is a more established figure in the superhero community in the DC Heroes Rebirth universe, but otherwise her presence in the story does not change dramatically.
The Spies
In the DC Heroes Rebirth continuity, Mark Shaw has an established history as Manhunter and is far more well known to characters like Superman and Batman. His motivations, abilities, and actions in the Event Leviathan story do not change significantly, only the reactions of others once his identity is revealed would be different. Lastly, Lois Lane's father, General Sam Lane, does not play a direct role in this version of the story. In the DC Heroes Rebirth timeline Sam Lane is already dead, having committed suicide to avoid a war crimes trial, and had already faked his death once before. The information that served as an impetus for Shaw's actions can have been found posthumously, and the clue that he left for Lois can have been part of a contingency plan put in place before his death rather than provided directly from him.