John Barrowman's Malcolm Merlyn is about to make his big return to "Arrow." Speaking to CBR, executive producer Wendy Mericle revealed that Merlyn will play a crucial role in the episodes leading up to the Season 5 finale.

"He’s going to be a huge factor leading up to the finale," she shared. "This season is all about legacy, and when Malcolm comes into the story, it’s really rooted as much by necessity from Oliver’s point of view as it is about what Malcolm means to him and what Malcolm means to Thea. It’s a great story, because it’s going to have a lot of action but it’s also going to have this kind of emotional undercurrent that is going to lead to a really big, huge series moment for him. I think it’s a great story to tell, and it’s great stuff for John [Barrowman] to play."

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Merlyn was an ever-present threat through the first four seasons of "Arrow." This year, however, he switched tracks and became a major villain on "DC's Legends of Tomorrow." There, he teamed up with Reverse Flash, Damien Darhk and Captain Cold to form the Legion of Doom. Together, the Legion searched for the Speak of Destiny and were successful in using it to change reality -- that is, until they weren't. The Legends went back in time, breaking a major rule of time travel, and circumvented the circumstances so that the Spear never ended up in the Legion's hands. Defeated, Merlyn was then deposited back in the time he was taken from.

As such, Merlyn was a little too busy to antagonize Oliver and Team Arrow, but that doesn't mean he's been completely absent from the series. He appeared in a flashback in the "Arrow" episode "Kapiushon," which found him striking a deal with Dolph Lundgren's Konstantin Kovar. However, he hasn't been spotted in "Arrow's" present day for quite some time.

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Last July, Barrowman struck a deal with The CW that makes him a recurring character on "The Flash," "DC's Legends of Tomorrow" and "Supergirl" as well as "Arrow." Over the course of "Arrow," he was a member of the League of Assassins, even rising to become R’as al Ghul before Nyssa al Ghul dismantled the organization.

Starring Stephen Amell as the Emerald Archer, “Arrow” airs Wednesdays at 8 pm ET/PT on The CW. The series also stars Emily Bett Rickards, David Ramsey, John Barrowman, Willa Holland and more.