A new plot synopsis for the upcoming ninth episode of the second season of The CW's "Arrow," the show's mid-season finale, suggests the inclusion of another major DC villain. Here's the synopsis:
"After a fight with Cyrus Gold (Graham Shiels), Oliver is drugged and left for dead. Determined to cure him, Felicity makes a risky decision. The cure causes Oliver to hallucinate, and what he sees forces him to confront his past.
Meanwhile, Barry Allen (Grant Gustin) continues to help Felicity, and their connection grows stronger. The Arrow asks Lance to look into Gold, but when the stakeout on Gold goes bad, someone is killed."
In DC comics lore, Cyrus Gold was the human name of the man who would become the zombie-like Batman villain Solomon Grundy. It's unknown at this time if we'll see Gold turn into Grundy within the context of the series.