• The cast of 'Arrow' and 'Flash' attend a special screening for the CW's 'Arrow' And 'The Flash' at Crest Theatre on November 22, 2014 in Westwood, California.

The cast of 'Arrow' and 'Flash' attend a special screening for the CW's 'Arrow' And 'The Flash' at Crest Theatre on November 22, 2014 in Westwood, California. (Photo : Getty Images/ Joshua Blanchard)

When "Arrow" Season 5 hits television this fall, viewers will finally get to see the Bratva storyline unfold. This integral aspect of Oliver Queen's backstory unveils how he became the skilled warrior and killing machine he currently is.

Flashback is an essential tool throughout the "Arrow" narrative. Going back and forth between Oliver's past and present allowed viewers to understand how the past led to present-day situations. "Arrow" Season 5's flashback will focus on Oliver's service as a member of a Russian mafia called Bratva.

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Although it's been mentioned several times on the show, what happened to Oliver in Russia still remains very much a mystery. How he learned to speak Russian and earned that Bratva tattoo is something that hasn't been fully explored. "Arrow" Season 5, however, is going to shed light on this big mystery, and "Arrow" producer Wendy Mericle teased that it will be a very dark journey.

"We really wanted to go gritty, dark, and make it feel very real," Mericle told TVLine. "We're dealing with the Bratva, and the Bratva is, as we all know, a pretty interesting and messed-up institution."

To give the story an authentic taste, Mericle studied documentaries about the real-life Bratva and "how they operate in Russian prisons."

In "Arrow" Season 5, leading the Bratva is "The Expendables" star Dolph Lundgren. His character is described as a "government strongman" who is "scary and formidable."

Aside from the Bratva storyline, "Arrow" Season 5 may also introduce the famed group of vigilantes called The Outsiders. As previously confirmed, Oliver is training a group of vigilantes to prepare them for the worst that could come with their crime-fighting activities. He suffered a lot when Laurel died, so he doesn't want these rookie vigilantes to have the same fate as her.

When asked if this group of vigilantes will be introduced as The Outsiders later on the show, Mericle told Collider that they haven't talked about that aspect of the show.

"The theme of the season is legacy," Mericle said about the show's core element this season. "He's gotta figure out what's really going to be his legacy and how he's going to honor what he set out to do, which is right his father's wrongs."

Perhaps, forming a solid group of vigilantes will be one of Oliver's legacies.

"Arrow" Season 5 premieres on The CW on Oct. 5.