SPOILER WARNING: This article contains major spoilers for "You Have Saved This City," the Arrow Season 7 finale.
The Monitor has come to collect. In "You Have Saved This City," the Arrow Season 7 finale, Mar Novu appeared at Oliver and Felicity's safehouse. He aimed to make Oliver make good on his end of their deal, informing him that they would travel to other worlds to warn of the upcoming Crisis. Worse, he revealed Oliver would die in the conflict to come.
By the time the Monitor showed up, Mia was already a few months old. He interrupted a discussion between Oliver and Felicity, where they laid plans to regain custody of Oliver's son William. They heard a floorboard creak and Oliver, ever vigilant, grabbed a knife off the counter. When he turned the corner, he found Mar Novu in the doorway.
"I thought I had more time," Oliver said softly. The episode flashed back to this year's Arrowverse crossover, which revealed the nature of his deal with the Monitor. In exchange for saving Barry "The Flash" Allen and Kara Danvers, aka Supergirl, Oliver promised to give "whatever the multiverse requires to survive the Crisis that is looming, when it is time."
Asked what the multiverse requires, Mar Novu replied, "You assist me as we seek to prevent the inevitable... The multiverse is more complex than you could fathom. I've seen your future, Oliver, inexorable and unavoidable. I have watched you die."
"During this Crisis?" Oliver asked, to which the Monitor replied with a solemn nod. "I am truly sorry," he added. A flash-forward confirmed Oliver's death; Felicity and her children visited Oliver's gravestone, which bore the year "2019" as his date of death.
"I cannot prevent his passing, but he can prevent the deaths of countless more, including you and your daughter, but he needs to come with me tonight," the Monitor explained in the present. He gave Oliver enough time to say goodbye to Mia and Felicity. Through his tears, he asked Felicity to keep Mia and William safe and to tell Mia that he loves her every day. With that, he left with the Monitor.
Since the Monitor has recruited Oliver for the cause, the Green Arrow may serve a role similar to Harbinger. In the comics event Crisis on Infinity Earths, Harbinger assisted the Monitor in testing and recruiting superheroes and villains to fight the Anti-Monitor. Unfortunately, Harbinger became corrupted by the Anti-Monitor and eventually killed the Monitor. She ultimately sacrificed herself to save the last three universes in the multiverse from certain destruction. If Oliver were to go out, this would certainly be an appropriate write to write off the Arrowverse's original hero.
Airing Mondays at 9 p.m. ET/PT on The CW, Arrow stars Stephen Amell as Oliver Queen, David Ramsey as John Diggle, Emily Bett Rickards as Felicity Smoak, Rick Gonzalez as Wild Dog, Juliana Harkavy as Black Canary, Colton Haynes as Arsenal, Kirk Acevedo as Diaz and Katie Cassidy as Black Siren.