During a Facebook Live chat last week, Stephen Amell revealed a very intriguing Arrow spoiler. The star said that the upcoming fifth season would feature an appearance by "someone that we haven't seen in two full seasons."

Many fans immediately suspected Amell was referring to Slade Wilson (Manu Bennett). However, Slade briefly appeared in Season 3, which (unfortunately) takes him out of the running. So who does that leave? There are a few possible candidates.

Anatoly Knyazev
If you don't remember who Antoly (David Nykl) is, that's OK. He appeared in Season 2's flashbacks when he befriended Oliver during their imprisonment on Lian Yu. He also appeared in Season 2's present day storyline when he helped Ollie break Lyla (Audrey Maria Anderson) and Diggle out of the gulag prison. And Antoly just so happens to be the leader of the Bratva, a Russian mafia organization. Earlier this year, executive producer Wendy Mericle teased that Season 5 will show "how Oliver got that Bratva tattoo and how he learned to speak Russian," which gives a lot of credence to Antoly being the one to return.

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The Huntress
We haven't seen Helena Bertinelli (Jessica de Gouw) since she was imprisoned after the death of her father in Season 2, and it would be interesting to see where the Huntress goes next. She no longer has anyone to seek vengeance on, so does that mean she could reform? Or will she get dragged back into the dark side and have to face off with Oliver once more? Either way, the Arrow producers have been very open about wanting to bring the Huntress back, so it wouldn't be very shocking if she popped up in Season 5.

Walter Steele
Even after Walter (Colin Salmon) and Moira (Susanna Thompson) divorced, he maintained a good relationship with his ex and her children. However, Walter hasn't made an appearance since the Season 2 finale. Oliver's rise to mayor could provide a perfect opportunity for him to return and dole out some sound, ex-step-fatherly advice. (He was once offered the mayoral position and declined, after all.)

China White
The Chinese Triad was a huge part of Arrow's second season, but ever since one of its leaders, China White (Kelly Hu), was imprisoned, they've completely disappeared. Now that Oliver's mayor of Star City, it could be fun to see how he would deal with China White's organized crime ring from both a vigilante and political perspective.

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Robert or Moira Queen
Before you write this theory off, yes, I know they're both dead. And yes, I know they both technically appeared in Season 3's "The Return." However, since Oliver's visions of Robert (Jamey Sheridan) and Moira were so fleeting and didn't include any new footage, I'm not sure that 100 percent counts. And now that The Flash has completely rewritten history thanks to Barry's (Grant Gustin) decision to save his mother's life, maybe one or more of Oliver's parents could also be alive in this new timeline!

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