Designated Survivor actor LaMonica Garrett has been cast as DC Comics character The Monitor in the 2018 Arrowverse crossover. The crossover will be titled "Elseworlds" and will take place across three shows: Arrow, The Flash, and Supergirl. This year, Legends of Tomorrow will be excluded from the three-night event.
The upcoming crossover will send the Flash, the Green Arrow, and Supergirl to Gotham City where viewers will be introduced to Batwoman, played by Ruby Rose. While the Arrowverse has referenced Bruce Wayne in the past, this will be the Arrowverse's first foray into Gotham City, which is one of the most important corners of the DC Universe. Tyler Hoechlin, who played Superman in season 2 of Supergirl, will be along for the ride as well.
TVLine reports that LaMonica Garrett will play a character named Mar Novu, aka The Monitor, in the crossover. Garrett's character is described as an "extraterrestrial being of infinite power". It's not been made clear if The Monitor will be an enemy or an ally to the heroes of the Arrowverse, but his inclusion does provide at least some clues as to what the story may entail.
In DC Comics, the Monitors are powerful entities who take it upon themselves to observe all occurrences within the Multiverse, including all realities and different points in time. The Monitors actually have a lot in common with the Watchers from Marvel Comics. One particular member of the group, who is simply referred to as The Monitor, was originally seen as an ally of supervillains, but eventually began using his knowledge to help heroes save the Multiverse when necessary.
Both Garrett's character and the name "Elseworlds" implies that the event may focus heavily on the Multiverse, or the various alternate realities that exist within the Arrowverse. This could explain the involvement of Supergirl and Superman, since Supergirl takes place in a different universe. The Monitor could serve as a villain, or he could be the force that brings them all together. It's possible that the Monitor will alert the heroes to a threat that could endanger the Multiverse as a whole.
The Monitor joins a growing list of DC Comics characters set to receive their Arrowverse debut in the crossover. The Elseworlds crossover will also introduce Bitsie Tulloch as Lois Lane, Jeremy Davies as Dr. John Deegan, and Cassandra Jean Amell as Mr. Freeze's wife. So it's only natural that someone like The Monitor join the fold as well.
The Flash season 5 premieres October 9, followed by Supergirl season 4 on October 14, and Arrow season 7 on October 15.