The Arrowverse's "Crisis on Infinite Earths" will include the Spectre, a DC Comics hero who plays a significant role in the comic book event of the same name. In the comic books, Spectre is Jim Corrigan, a murdered police detective who becomes the host of the Spirit of Vengeance, a cosmic entity whose duty is to punish people who commit evil acts. As the Spectre, Corrigan is easily one of DC's most powerful heroes, along with Superman, Martian Manhunter, and Shazam. In fact, some may argue that Spectre is superior to all of them.
The five-part Arrowverse crossover "Crisis on Infinite Earths" will encompass Arrow, The Flash, Legends of Tomorrow, Supergirl, and its freshman series, Batwoman. The crossover will also manage to incorporate the worlds of Smallville, the short-lived CW series Birds of Prey, Black Lightning, and more. "Crisis" contains a growing list of guest stars from other shows like Smallville's Superman (Tom Welling) and Lois Lane (Erica Durance), Ryan Choi (Osric Chau), Robin actor Burt Ward from the 1960s Batman series, and longtime Batman voice actor Kevin Conroy.
The latest addition to the cast is Stephen Lobo as the Spectre. Lobo was a series regular on the science fiction series Continuum for four seasons. Nothing has been confirmed about how Lobo's character will factor into "Crisis", but the answer may be found in the source material. In the comic book version of "Crisis on Infinite Earths", Spectre plays what Arrowverse executive producer Marc Guggenheim agrees was a "pivotal role". As one of DC's most formidable characters, it makes sense that Spectre would be a hero capable of turning the tide, as he was instrumental in uniting the superheroes and supervillains of the Multiverse against the Anti-Monitor.
In the comics, the main villain of the "Crisis" is the Anti-Monitor (LaMonica Garrett), whose goal is to destroy the Multiverse. The Anti-Monitor is believed to be dead after his battle with Supergirl, who dies in their confrontation. It's the Spectre who lets everyone know that the Crisis isn't over and that the Anti-Monitor still lives. He uses his power to announce his existence to all the remaining timelines. The Spectre explains that the Anti-Monitor has traveled to the beginning of time itself to rewrite history. Thanks to the efforts of the Spectre, the heroes gather together and follow Anti-Monitor to the past for an epic battle. A fight between two characters as powerful as Spectre and the Anti-Monitor results in the merging of all the timelines. This stops the Anti-Monitor from achieving his ultimate goal, but even so, it isn't a desirable outcome for the DC Universe.
Since the Monitor, the Anti-Monitor, and possibly Pariah (Tom Cavanagh) appear to be taking the same roles as their comic book counterparts, the same may be true of Spectre, which is not a good sign for all the different universes in the Arrowverse. It may mean that the TV version of the "Crisis" may indeed move in the same direction as the comic, which would merge the various Earths together. If so, the lives of numerous Arrowverse heroes and villains may be the cost.