Arrow is bringing two characters back from the dead. Colin Donnell and Josh Segarra, who play Tommy Merlyn and Adrian "Prometheus" Chase respectively, will return for Season 8.
"Adrian Chase comes back in a different way than expected," showrunner Beth Schwartz told Entertainment Weekly. "We're really excited about that because obviously he's one of our favorite villains."
On the subject of Tommy Merlyn, executive producer Marc Guggenheim promised Donnell is "not coming back as the Tommy we know."
Donnell's Tommy died all the way back in Season 1 during the Undertaking. When his father Malcolm launched his plans to destroy the Glades, Tommy was collateral damage. He was killed when a building collapsed on him, but not before he reconciled with Oliver and set the Green Arrow on a new, non-lethal path.
Since then, Donnell has reprised the role several times. He resurfaced in the fourth Arrowverse crossover "Crisis on Earth-X," where he played an alternate reality version of Tommy that became Prometheus. Throughout the years, he has appeared in flashbacks and as a hallucination; most recently, he returned for Season 7's "Living Proof" as a symptom of Oliver's concussion. He also became one of the Human Target's disguises in the Season 6 episode "Docket No. 11-19-41-73."
Segarra's Prometheus, on the other hand, died by his own hand as part of his quest for revenge. In the Season 5 finale, he shot himself in the head; this triggered a fail-safe explosion on Lian Yu that killed Samantha Clayton, the mother of Oliver's son William. He returned in Season 6 episode "Fundamentals" as a hallucination.
Now that Oliver is working with the Monitor, though, anything is possible. Debuting in last year's crossover "Elseworlds," the Monitor proved himself to be a near-omnipotent, world-hopping being. As such, Tommy and Prometheus could be alternate world versions of the characters that appeared on Earth-1. What's more, time travel has long been established on the series, so it's possible the characters will be plucked from elsewhere in the timeline. Indeed, their returns may have everything to do with "Crisis on Infinite Earths," this year's five-show crossover.
Returning Tuesday, October 15 at 9 p.m. ET/PT on The CW, Arrow stars Stephen Amell as Oliver Queen, David Ramsey as John Diggle, Rick Gonzalez as Wild Dog, Juliana Harkavy as Black Canary, Colton Haynes as Arsenal and Katie Cassidy as Black Siren.