Let's be clear, everything I'm going to talk about is purely speculation and I could be totally wrong.
Earlier today, Variety announced that Ryan Robbins (Falling Skies) has been cast in [Arrow](tag:720988) Season 4. He will play Concklin, a really minor villain in the comics. He will be an enemy of Oliver in the flashbacks. They gave a detailed description of his character.
"Robbins will play Conklin, a sadistic and ruthless member of Shadowspire who will be an adversary for Oliver (Stephen Amell) in the flashback sequences."
We already know that the Baron Blitzkrieg has been cast and will be the main opponent of Oliver in the flashbacks.
Here, we officially got the confirmation that the organisation Shadowspire will be part of the show.
Shadowspire is a powerful criminal organization supplying South American cartels with weapons and all sorts of high-tech technologies. Their influence extend to every corrupt governments.
They first appeared in Deathstroke #53, where the mercenary stopped them from unleashing a plague on Washington DC.
Now, let's talk about why I'm thinking Shadowspire could be linked with...
The immortal caveman is the all reason of this theory! Savage has been established as the "big bad" of [DC's Legends of Tomorrow](tag:2937021) and I have reasons to think we might see him a way long before the series starts.
We learned during San Diego [Comic-Con](tag:1029427) that the Legends plot would be introduced in both Arrow and The Flash. They didn't say anything about flashbacks.
In the comics, Shadowspire is allied with Vandal Savage's organization, Symbolix. They, together conducted experimental research with the objective of using cell samples of the Justice League to reproduce their powers. This ultimately lead to the creation of a new hero, Damage.
Stephen Amell said that during those five years away, Oliver saw unimaginable things dealing with magic and powers. Thus, we could see a thousand years man being mentioned maybe even a glimpse at him.
I was thinking of how the writers could introduce Vandal Savage on this universe and I think Arrow would be the better choice to do so. The show already dealt with the notion of immortality and will even more with Damian Darhk.
The darker tone also seems to fit more with a character like Savage. But it's only what I think.
Here's the end of my theory ! Thank you for reading and if you have another idea in mind, I'd love to hear it !