The CW drama seriesThe 100is back for its fifth season, with Clarke (Eliza Taylor) struggling to survive on Earth while her friends in space think they may have finally figured out a way to get back to the ground. At the same time, a new ship of prisoners – this time made up of some really bad criminals – has landed and is led by a woman (Ivana Milicevic) whose motives do not immediately reveal themselves, but clearly are a threat to anyone that crosses her path.

During this 1-on-1 phone interview with Collider, showrunnerJason Rothenbergtalked about what fans can expect from Season 5, how this season started to take shape, why the six-year time jump provides a bit of a reboot, the challenges of the premiere episode, the threat of this new group of prisoners, the eventual reunion between Clarke and Bellamy (Bob Morley), which character has had the biggest character journey in the six years that have passed, the biggest threat in Season 5, and his plan for the series, going forward. Be aware that there are somespoilersdiscussed.

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Collider: How close does this season look to you what you thought it might look like, if you actually got to this point?

JASON ROTHENBERG: When we first started, when I wrote the pilot, I was just trying to get a series order. I hadn’t thought about anything. I knew there were people on Earth, obviously. We had the spear come out of the woods and kill Jasper. He literally was dead in the pilot script. That didn’t end up happening and that spear barely missed his heart. So, I knew there were survivors on the ground, but I didn’t have any idea what that culture was. Ultimately, I fairly quickly began to build out the world and what it was. Every season, as I’m breaking, with the writers, the season that’s currently being produced, I’m always thinking about what the next season is, so that we can begin to plant the seeds of what that might be. That way, the ending can take us there. And also, to keep it creatively interesting for me, I like to change it up, radically, every season. But we’re beyond the point that I initially envisioned, as an end point, at this moment. That’s fine. It’s elongated, in terms of where the story’s going now. Wait till you see where it goes, at the end of Season 5. We’re talking about a change that will make the last change look like nothing. It’s really, really exciting, where it could potentially continue to go, and that’s how we keep it interesting for all of us, and the audience, too.

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Are you at a point where you have to think about how much further, realistically, you see the show going? Do you have a plan for a certain amount of seasons more, or are you taking it season by season?

ROTHENBERG: Well, yes and no. I definitely feel like I have a plan in mind. I’m not gonna say what the plan is, at this point, but it does have this nice ability to elongate, and by that, I mean we can push that out, as far as we need to or as far as we’re lucky to. I’m not sure how much more I have in me. Its been a very, very long run. I feel like I’ve been blessed in playing with winnings, as they say in the casino, for awhile. At some point, it’s a business decision, as much as it is a creative one. I also don’t want the show to stick around, past its sell by date. I feel like, as of now, it functions as a really great five-season show, and I have a great idea for Season 6. As long as we continue to come up with what I think are great ideas and stories I’m excited to tell, and that keep everybody inspired, then we’ll keep doing it.

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Does this season feel like a re-invention for you, especially as the showrunner, or does it just feel like the next step in the story?

ROTHENBERG: It feels like the next step in the story. Every season for me is so different. The story of the season is always its own unique thing. This one had some added obvious evolution, in the idea of the time jump and how different the characters can be, based on those six years spent changing while we were away, so in that way, it is a little bit of a reboot. It’s definitely presented interesting challenges that hadn’t existed in prior seasons, but there were things that we were excited about and I feel like we handled well. The audience will be the judge, but I think this season is easily one of our best.

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What were the challenges you were most excited about, in doing a premiere episode with really only one actor for the majority of it, and what were the challenges that you were dreading?

ROTHENBERG: I never, ever was dreading. I always thought, “Oh, my god, this is a huge idea and it’s totally unique and not like anything we’ve ever done before.” I feel like the idea of her being the omega woman - the last person on Earth – was baked into a cake, in terms of the way we ended Season 4. The idea of getting to play with that, and getting to see Eliza [Taylor] in that tour de force, was really exciting to me. Obviously, we all know how good she is, but I still think she hasn’t even scratched the surface of how good she is. This was really an opportunity to get her to shine and showcase her for 20 minutes. Not a lot of actors could pull that off. She’s special.

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Clarke is faced with a new ship landing that contains a whole new group of prisoners, and these are prisoners that really feel like prisoners. At the center of that is a leader who’s more strategic and commanding than just a general prisoner. What can you say about the addition of Ivana Milicevic, as Charmaine Diyoza, and what she brings to the season?

ROTHENBERG: Ivana is special, too. I’m really excited about people getting to see what she’s doing on the show and how good she is. Interestingly, you’re right, she’s a real prisoner. She committed some pretty horrible acts that got her arrested and set off to this penal colony in space, where they were mining an asteroid, but she is also strategic. The thing about Ivana that I don’t know that people realize – or maybe they do, but I certainly didn’t – is that she’s hilarious. She’s a comedienne. She’s got things that she does with her face, all the time, that are just perfect. You don’t necessarily write some of those moments, like when she lifts her eyebrow in a certain way, or she tilts her head in a certain way. It just instinctively softens. What I mean by that is that you know she’s the bad guy, as far as bad guys go, but we have a tradition on the show of dimensionalizing our bad guys towards the light side and dimensionalizing our good guys towards the dark side. We live in the gray, all the time, and I would say that she certainly fits in that category, but these little gestures that she does make you smile and make you like her. She’s a bit of a shapeshifter. You’re not sure whether or not to like her or trust her, and that’s what I like about the character.

Clarke and Bellamy’s eventual reunion is something that a lot of people are looking forward to, but obviously that won’t come immediately because everyone is so separated. What can you say about them and that moment, and how eventually meeting back up will change their dynamic?

ROTHENBERG: Well, Bellamy has no idea she’s alive, so that’ll blow his mind, emotionally. Obviously, Clarke is in a pretty bad way when Bellamy shows up, in time to save the day. When they’re back together again, a lot of things have changed. Clarke now has Madi to worry about, and Bellamy is now deeply, deeply bonded to the people in space kru. It definitely complicates their relationship and makes things interesting, going forward.

Who would you say has the biggest or most surprising character journey, this season, especially with what they’ve experienced in the six years that they’ve been apart?

ROTHENBERG: I think a lot of them are significantly changed, but I would say Octavia (Marie Avgeropoulos) is easily the one that is the most dramatic. She’s certainly the most different form who we’ve come to know, and that has the most impact, negatively and positively, on the plot, going forward.

This season feels really big and really widespread, with everyone in their separate places and groups, whether it’s on the ground or underground or in space. What has been the biggest production challenge, specific to this season?

ROTHENBERG: It’s really hard to turn Vancouver into a dessert, so that was hard, for sure. You’re right, it’s an epic season. Ironically, it’s focused on a pretty simple idea, which is that there’s one survivable valley left on Earth and everybody wants it. If they can somehow figure out a way to link arms and live happily ever after on it, then that would be great, they could make it. But we’re human beings and we have a tendency to want to do what’s best for ourselves, our sides, our country, our people. That’s the story we’ve been telling, in one shape or another, from the beginning.

Obviously, it’s easy to think that these new prisoners will be the biggest threat of the season, but have we even seen the biggest threat of the season yet?

ROTHENBERG: I would say that it’s all about perspective. They are a threat, for sure, and some of them are genuinely criminal, dangerous people, unlike the hundred, for the most part. Dax was a real genuinely bad guy. But in terms of the villain of the season, when the story is said and done, Octavia may be. Some people might consider her the villain of the season, as opposed to these new prisoners. There’s no debating the fact that McCreary is just a bad guy. I think people will be torn. Certainly, Shaw is not gonna be considered a bad guy. I think The CW’s poster is perfect because it says, “No heroes, just survivors.”

The 100airs on Tuesday nights on The CW.