Brandon Routh has been a part of the DC Multiverse for over fifteen years now. He first caught the world’s attention in 2006’s Superman Returns before returning to take on a different hero—the Atom—on Arrow in 2014. Routh would continue to play the affable Ray Palmer for another six years, most of them on the time-traveling superhero satire DC’s Legends of Tomorrow, until saying goodbye to the role in the show’s fifth season. So, what would cause him to end his superhero retirement so soon?

Why, no less than “Armageddon.”

Routh’s Atom will play a key role in the five-part event that kicks off The Flash’s new season, offering fans a chance to discover exactly what he’s been up to since saying goodbye to the Legends and saying “I do” to Nora Darhk. But don’t expect a lighthearted reunion. Threatened by no less than Despero, the conqueror of worlds who has held his own against the entire Justice League, Ray will be pushed to his limits, and without the reassurance of an ongoing series to return to, survival for the returning hero isn’t guaranteed. Could this be Routh’s final DC adventure?

We’re not about to say…largely because we have no idea. So, we sat down with Routh to see what we could learn about his return to the Arrowverse, what sort of threat Team Flash is facing as their season begins and how Routh feels about playing optimistic heroes in an increasingly cynical world.

When you left DC’s Legends of Tomorrow in season five, did you ever think you’d be returning to the role of Ray Palmer?

I thought there was a possibility that Ray could come back. I certainly thought that was a bigger possibility than with Superman, but then that happened, so I thought, “Well, if Superman could come back, then there’s definitely the possibility of Ray coming back at some point.” I was surprised, though, that it was on The Flash.

The first call I got was about appearing on The Flash. That happened and then it must have been three or four weeks later that I got the call about the Legends 100^th episode.

Was it easy to get back into the role?

Yeah, it was actually easier on The Flash than it was on Legends in some ways because Flash is a through line story. The episode is largely about Ray and him helping Team Flash, and also what his journey has been since he left the Waverider and where his mindset it. It gets changed a little bit for the better through the journey he goes on in the episode.

With Legends, it was kind of like a flashback episode. We were revisiting older versions of the characters and there were many people in the scenes—it’s different to shoot that way, a multi-person scene versus a scene with just a couple of people moving the episode forward. It wasn’t hard, but it was a little bit different and also strange to be on that set as a guest star and not a series regular. But it was really great to see all of the crew that’s still there and all my cast mates and friends over there.

The threat in “Armageddon” is more serious and less silly or tongue-in-cheek than what we’d typically see on Legends of Tomorrow. Does that change how you approach the character at all? You’re probably not going to be channeling Mister Rogers when you’re battling Despero…

Well, Ray is Ray whether he’s on Flash or Legends. Stuff like the Mr. Parker episode, it’s a caricature and a heightened reality. Those are just fun. But Ray on Flash during “Armageddon” is the same Ray as in Legends. It’s the scene and the stakes that are at play that change his demeanor, and even in a high-stakes moment, one of my favorite things about Ray is that he’ll still crack a joke or say something to break up the tension. I think that’s great for the characters, but also for the audience since you’re not just mired in heaviness the whole time. I love that duality.

But Ray can be serious when he needs to be serious. He’d much rather be happy, joyful and exuberant, so he’s that most of the time unless duty calls and then he puts his game face on and buckles down.

Speaking of putting your game face on, how dangerous is Despero going to be for Barry and Team Flash?

He’s incredibly powerful. His abilities far outweigh the Flash’s abilities and powers. It’s incredibly daunting, and it’s only with Ray’s help that Barry escapes and is able to take a breather in order to come up with a future plan for the next episode. I think things stay pretty much by the skin of their teeth each episode until we reach the conclusion and they’re able to figure out a way to deal with him.

Ray Palmer hasn’t really interacted with Barry Allen all that much. What sort of relationship can we expect to develop between these two?

There haven’t been a lot of moments. I think one of the most poignant moments that Ray and Barry have had is when Ray tells Barry that Captain Cold has died. I think that’s in the crossover with the Dominators. There are also some fun scenes in the first episode Ray was in on The Flash. But they haven’t had a lot of one-on-one interaction or opportunities to fight together. There are a couple of fun moments during the fight in tonight’s episode where they have some good banter and we see some cool Atom powers that help Barry—stuff that we don’t often utilize. Or rather, it wasn’t utilized as much as I would have liked because of the expense of the Atom special effects. But they use it in this, which is pretty fun.

I think Barry sees Ray as more of a partner now. It’s a partner-to-partner type of energy, where at the beginning, Barry was learning how to be a leader and how to be a superhero. Ray certainly didn’t know either, but he came from the business world where he was a leader, so maybe Ray was a little bit more of a mentor in some ways to Barry and Cisco. Now, with this episode, Barry’s matured a lot and upgraded his abilities and leadership skills over the years, so they feel a little more evenly matched, which is kind of cool.

Probably more than any other character in this shared universe, Ray Palmer is an idealist and an optimist. There’s almost an innocence to him that’s persisted throughout his time on the Waverider. Do you feel superheroes like that are particularly important right now? And have you ever wanted to see him get his hands a little more dirty?

Ray has gotten his hands dirty, actually. It just never was discussed. I think it was in an episode of Arrow where Ray rockets through a plane—an ARGUS plane or something—and destroys it and everyone in it. There’s also a moment in Legends where he zips through a guy’s heart in the Western episode and kills him, and we never deal with that! There was never any, “Oh my god, I killed somebody!” So, those were certainly moments that could have been an opportunity for Ray to have to deal with them and process them. He’s also had his moments of ego and selfishness, like when he gives Nate the super serum. He was the one who was supposed to be the real hero, but then he loses his suit and he’s upset with Nate for destroying it. There are a few of those moments.

I definitely think it’s important to show duality, light and dark, and how not everything is hunky dory and happy. But the overriding thing that is important to me is Ray’s idealism and his belief in the possibility of a better life and a better society, and of helping people. Somebody has to uphold that because if nobody else is holding that vision of the world, then it doesn’t exist. Is it over the top? Is it too much? Quite possibly and you have other characters who balance him out. But that’s what makes him so great and appealing to me.

I’m so happy to uphold that. Of course, that comes from Superman as well—he’s the #1 boy scout of them all. But it’s different coming from Ray, who doesn’t have superpowers. He has a super-powered suit, but he doesn’t have inherent powers. So, for him to still believe that way is for all humans to believe that way, in the possibility of greatness, upgrading and evolving positively.

"Armageddon" debuts tonight on The Flash at 8 p.m. (7 p.m. CST) on The CW. For all the latest news, features and announcements out of Central City, visit our official Flash series page.

Not sure what's been happening in the Arrowverse? Don't worry, we get you caught up on all you need to know ahead of "Armageddon" in this one easy-to-read primer.