Last night on Arrow, audiences might have been sad for a departure, but they were also surprised to learn of a surprising return: Vertigo, the designer drug that has been largely absent from the Arrowverse in recent years, is back in a big way, as Ricaro Diaz has taken over the Vertigo trade in Star City.
Vertigo was first introduced in the show's first season, and was a significant force under the stewardship of Werner Zytle, who would become known as Count Vertigo, taking on the name from Cecil Adam, a drug dealer who had designed it but only faced off against Oliver briefly before his death.
Vertigo is a deadly narcotic that makes its users disoriented, leading to a dizzying, powerful high. In the first season, Thea took the drug at a party, crashed her car, and The Hood tracked down its dealer to put him out of business.
Zytle would discover a way to weaponize it against Team Arrow: When injected directly into the blood stream while in its purest form, Vertigo affects the thalamus, where all the information from the pain receptors are collected. This then causes the victim to believe that they are in excruciating pain. The effect can last for days, until the heart just gives up and stops. With the version introduced by Werner Zytle, Vertigo not only induced excruciating pain, but also made the user hallucinate their greatest fear.
This, of course, is likely to prove a useful weapon against Team Arrow in the hands of a conniving villain like Diaz, especially as Oliver continues to pare back his operation, alienating his team and ending up largely alone.
Vertigo is not the only throwback to the show's earliest days to make an appearance in an upcoming episode: Tommy Merlyn, played by Chicago Med's Colin Donnell, will apparently have an appearance in one of the season's final installments, according to a tweet from series star Stephen Amell.
He could, one guesses, be a Vertigo-inspired hallucination, although Amell's comments about a flashback seem to make that less likely.
Arrow airs on Thursday nights at 9 p.m. ET/PT on The CW, following episodes of Supernatural.