Arrow Season 3 Spoilers: What Is This Mystery Set for the Season Finale?

Fans of the CW's Arrow who follow showrunner Marc Guggenheim on Twitter may have noticed he has tweeted a handful of pictures regarding a giant "mystery set" for use in the finale.

The "Ask Ausiello" column at TVLine has some scoop on the set directly from the man himself:

"Remember that mystery set that was constructed for the finale? Guggenheim teases that it will play host to R'as, Nyssa and Oliver, and will likely not be seen again beyond the May 13 closer, because 'it requires a fair amount of green screen work to make it work.'"

Interesting. Could it be an arena of some kind where the three do battle? Or maybe the setting for some sort of dream/fantasy sequence that would be too difficult to do practically? Leave your guesses in the comments section.

In case you missed it, here is the official description for next week's episode, "Al Sah-Him."

"THE LEAGUE OF ASSASSINS SETS THEIR SIGHTS ON NYSSA - Oliver (Stephen Amell) goes through a rigorous transformation. The League of Assassins sets their sights on Nyssa (guest star Katrina Law), who is back in Starling City training Laurel (Katie Cassidy). When Nyssa realizes they are coming, she arms up to face them alone but Laurel asks Felicity (Emily Bett Rickards) and Diggle (David Ramsey) to help protect her new friend. Thor Freudenthal directed the episode with story by Beth Schwartz and teleplay by Brian Ford Sullivan & Emilio Ortega Aldrich (#321)."

A new extended promo for next week's episode has been released, and it looks like Oliver is going to cross paths with his friends sooner rather than later, but in a way he'd rather avoid. Check it out below: