A crisis is coming to The CW in the form of "Crisis on Infinite Earths." Inspired by the DC comics storyline of the same name, the long-teased crossover threatends the existence of not just the world, but the entirety of the Arrowverse multiverse.

The event is certainly ambitious, especially for such a niché network, and it will irrevocably change The CW's superhero shows. For both diehard fans and those still catching up on streaming services, though, it can feel a bit daunting to keep up with everything leading up to the payoff. Some may even be tuning into the event after dropping out of the Arrowverse for a while.

With this in mind, here's a brief refresher on what event is about, who all is in it and what the main CW DC shows are doing to set the scene for the Anti-Monitor's arrival.

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WHAT IS CRISIS?

Like the original story, Crisis sees the heroic Monitor attempting to recruit heroes from various Earths and realities in an effort to stop his maniac brother, the Anti-Monitor, from destroying those worlds. The Anti-Monitor is pure evil incarnate; hellbent on extinguishing all life across the multiverse. The Monitor himself first appeared in the previous CW crossover, Elseworlds, and had warned of the coming Crisis even then. A newspaper clipping from the very first episode of The Flash did the same thing back in 2014.

Now, the battle will finally insue onscreen; combining the forces of multiple Flashes, Supermen and at a couple of Caped Crusaders.

ARROW

The very first series in the Arrowverse is coming to an end with an abbreviated final season, one which prepares its hero for the end. Tasked by The Monitor to recruit heroes throughout the multiverse as part of a team to face The Anti-Monitor, Oliver Queen finds himself revisiting locations and people from his past. This can be seen in the season's first episode, which radically warped Season 1's events but on Earth-2. Oliver must also face his supposed upcoming death, which is meant to occur in Crisis.

The season also continues the future storyline from Season 7 and will be upgrading series regular Lyla Michaels to her comic book status as Harbinger, who had a chief role in the original Crisis.

RELATED: Arrow: Lian Yu Is the Perfect Place to End Oliver's Journey

THE FLASH

Similar to Arrow, The Flash is spending much of its current season preparing its hero for the end. As seen in the pilot's ominous newspaper headline, Barry Allen/The Flash will likely die in the event, much as he did in the original comic book. Building the multiversal tension in the series is the death of world-hopping ally, Gypsy, too.

During Crisis, Barry will be joined by The Flash from the '90s TV series, played by John Wesley Shipp who also plays Barry's father on the CW series. Much of the season's themes come from life vs. death, shown in the seeming hopelessness of the hero's fate, and the ironic push that villain Bloodwork seems to be giving The Flash to live.

SUPERGIRL

Supergirl Season 5 Poster

Strangely enough, Supergirl has not laid much narrative ground for Crisis, aiming instead to develop its own independent storyline for this season. Numerous versions of her cousin will appear in the crossover, however, from a Kingdom Come version of the Superman Returns Superman, to the Supergirl Earth Superman, as well as the Smallville Superman.

Speaking of which, Supergirl does not live on the same Earth as The Flash and Green Arrow, nor does Black Lightning. If Crisis is anything like the Multiverse-undoing story which it is based on, they may find themselves retconned into being on the same Earth after all.

One way in which the show is setting up the event, however, comes from the return of Lex Luthor. Killed in the Season 4 finale, the villain has been brought back by The Monitor, of all people, and has finally surfaced in a recent episode. The maniacal scientist's brain may actually play a key role in stopping the greater threat of the Anti-Monitor.

RELATED: The Flash & Arrow Are Taking Similar Paths to Crisis

BATWOMAN

First appearing in last year's Elseworlds, Batwoman is the newest DC show to hit the CW so it wouldn't be fair for the newcomer to be saddled with Crisis set-up before getting a proper chance to establish its own identity. Instead, Batwoman has served as a prequel of sorts, taking place before Kate Kane's appearance in Elseworlds. Viewers could essentially skip her show for the time being if they simply desire to be caught up for Crisis, but there will be other Bat-characters in the event.

Kevin Conroy, who voiced Batman in the DC Animated Universe, will be portraying an elderly Bruce Wayne. Though this was incorrectly suspected as being based on Batman Beyond, the exoskeleton that the character is shown using means that this is actually the Kingdom Come version of Batman. Batman himself has not truly appeared in the Arrowverse in his full glory, so seeing an old Bruce Wayne may be the closest thing that fans get. His interaction with Kate Kane will be especially interesting since the Batman of her Earth seemingly abandoned Gotham City.

Burt Ward, who portrayed Robin in the 1960s Batman TV series alongside Adam West, will also be appearing in the crossover, but since his exact role isn't confirmed, it's unsure how he'll factor into Crisis or possibly even Batwoman. The other DC CW shows have so far been unrelated to Crisis in their plots, but there are supposedly even more fan-favorite cameos to be announced. Some of these will develop into larger storylines, such as when Ryan Choi becomes the new Atom.

In any case, every hero big and small in the Arrowverse will have a role to fill in the earthshattering event later this month.

"Crisis on Infinite Earths" begins Sunday, Dec. 8 at 8 p.m. ET/PT on Supergirl, then continues in Batwoman on Monday, Dec. 9 at 8 p.m. ET/PT and in The Flash on Tuesday, Dec. 10 at 8 p.m. ET/PT. After the winter hiatus, the crossover will conclude on Tuesday, Jan. 14 in Arrow at 8 p.m. ET/PT and in DC's Legends of Tomorrow at 9 p.m. ET/PT.

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