Battlestar Galactica alum Aaron Douglas will speed into The Flash as The Turtle, EW reports.
Douglas will debut the character in the forthcoming midseason premiere, titled "Potential Energy."
In the comics, The Turtle was a Jay Garrick villain, while a successor, Turtle Man, hounded Barry Allen on Earth-1.
That character, who could slow time to render Barry's speed irrelevant, will seemingly influence the TV version of the character.
EW reports that "on the show, the team hunts down this meta-human who can slow time itself."
"In a surprisingly funny twist, Cisco has actually been hunting The Turtle the entire series," executive producer Andrew Kreisberg told the magazine. "To Barry's surprise, everybody knows about Cisco's hunt for the great white whale, which is The Turtle; he's the only one who didn't know about it. We love the idea that there was a villain out there that they knew about, but they just haven't bothered to tell the audience about yet. All Barry wants to do is get faster, because if he can get faster, he can take on Zoom. He's going up against a villain who is literally slowing him down. This is one of our best episodes coming back that we've ever done. It feels big and emotional."
The Flash returns on Tuesday, January 19, at 8 p.m. ET/PT on The CW.