When the Arrow / Flash Spinoff was first announced back in February, it was revealed that the currently untitled show, which will debut in midseason, will feature Brandon Routh (Atom) and Caity Lotz (possibly her killed-off Black Canary character) from Arrow and Victor Garber (Firestorm) and Wentworth Miller (Captain Cold) from The Flash, with Dominic Purcell (Heat Wave) also joining the cast today. The initial announcement revealed that the show will also feature three DC Comics characters who have never been used in a TV series before, but it seems that there are actually four. Series co-creator Greg Berlanti told Variety that these three unspecified heroes will be joined by a mysterious villain, who has also never been portrayed on the small screen. Here's what he had to say below.

"(We're) making sure that the villain that we have on that show is distinct too... another big character who hasn't been used yet."

A casting breakdown that surfaced last week revealed that the three characters are currently being cast under pseudonyms "The Traveler," a "Han Solo-esque rogue" from the future, "Female Warrior," a young Latina who is "pretty but unassuming," and a "Mystery Hero," an African-American male in his 20s who "gains powers, and then, as part of the team, regularly quips about the insanity of the situations." While Greg Berlanti wouldn't offer any clues as to their identities, he did talk about the process of choosing these characters for the spinoff.

"In picking them, it was very much about picking, 'who are some of the most popular characters we've created?' and also, tonally, who went with who? How disparate could we make it? And we're also introducing these three new characters that we're casting right now. I think it's really important that we have another female hero on the show, and this one is really exciting. I can't wait for people to find out - we just have to cast it right, as always. And then you want that Rat Pack-y kind of vibe of all this crew hanging out, as disparate and as different as they are."

Greg Berlanti added that the whole series will have the same feel as the previously-aired crossover episodes between Arrow and The Flash, "where you feel that 'event-iness,' but all the time." He also compared this untitled show to a Western, where plenty of "lone gunman and sheriffs" are in the same town.

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"For us, first and foremost, with all of [our shows], it's about 'how is it its own thing?' Because we don't just want to do it to do it. Some people do that and then they're three episodes in, thinking, 'Why did we do this?' So for me, I compare the shows to old Westerns; we have a lot of lone gunmen and sheriffs in town, and this one is very much an ode to things like The Magnificent Seven or those great heist pics like Ocean's Eleven where you get all of those colors at the same time, and a true ensemble, and that was the fun of it."

Hopefully we'll hear about who all of these mystery characters are in the Arrow / Flash Spinoff very soon. What do you think about these new details? Do you have any theories about who this big DC Comics villain will be? Let us know what you think below, and stay tuned for more updates.