This coming season's Arrowverse crossover event "Crisis on Infinite Earths" is shaping up to be the shared universe's most ambitious yet, and returning star LaMonica Garrett is deep into preparation for reprising his omnipotent role.Garrett, who portrays the Monitor overseeing the DCTV Multiverse, shared a behind-the-scenes photo of himself online in-costume and reading Marv Wolfman and George Perez's classic comic book crossover that inspired the coming television event.RELATED: Can Crisis on Infinite Earths Be More than Arrowverse's Endgame?

Garrett debuted as the Monitor during last year's Arrowverse crossover, "Elseworlds," where he readied the Arrowverse heroes for an as-yet unrevealed threat to all of reality.

The Monitor would reappear briefly in several of the various Arrowverse season finales to continue to set the stage for "Crisis on Infinite Earths," escorting Oliver Queen to parts unknown based on a promise Green Arrow had made to him during "Elseworlds" to save the Flash and Supergirl's lives.

RELATED: Why Black Lightning Isn't Surprised About His Crisis on Infinite Earths Role

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