Spoiler warning: Don’t read on unless you’ve seen “Wanheda: Part One,” the Season 3 premiere of the CW’s “The 100.”

I shared a few thoughts on the return of the CW drama in this review, and I’ll have more to say about “The 100” later in season three. Executive producer and showrunner Jason Rothenberg addresses aspects of the new season and “Wanheda: Part One” below (and Rothenberg and members of the cast discussed what’s coming at a recent press event as well). Part 2 of this interview will be posted after the fourth episode of “The 100” airs. This interview has been edited and condensed.

The biggest thing I noticed about the early Season 3 episodes is the scale, the epic feel of some of the new sets. There’s a “Lord of the Rings” feel in some ways, in the storytelling and in the look of the show in Season 3. Why go to that bigger place?

That’s the kind of epic storytelling that I like. “Lord of the Rings” I loved. I love “Game of Thrones” still. The reason why [we did it] is because we could. [The characters] came down in season 1 and looked at [the world] through the keyhole — all we saw was that. What keeps me excited season after season is to put these people into new worlds and have them interact with new characters. The more they see of the world, the more we see of the world.

What do you feel you learned in the first two seasons? Over the course of telling those stories, what do you feel like you locked into what you want to keep on doing?

It’s a little disingenuous of me to say we found the show in [season one’s] episode four, because the truth is, I knew when we started that we were going to do the culling that season. Day one in the writers room, I said, “This is going to happen. And this is where we’re going.”

But in terms of finding the level of edge and the level of darkness and the level of grittiness, [that took some time to calibrate]. The pilot ended with a spear in the chest of one of our main characters, and it was supposed to kill him. But Devon was so good as Jasper that [we didn’t kill him]. At the time, we thought, “If we wimp out on this, people are going to kill us.” We needed to quickly figure out a way to find that place again — to get that credibility [about a willingness to kill off characters, otherwise] we’d lose a bit of that.

So at the end of episode three, we had the death of Wells, then we had the hanging of Murphy and then Charlotte jumping off the cliff. And of course, the culling. That was like, boom, boom, boom, episodes three, four, five — here we are and this is where we’re going to stay. We’re saying, “There is no right and wrong. The good guy is hard to pin down.”

We really pushed that in season two. At the beginning of the season, I knew Clarke was going to kill Finn, but I didn’t know how. I knew that at the end of the season, she was going to irradiate every man, woman and child in Mount Weather. There’s some fighting [about that as the story is shaped]. You’ve got to overcome the instinct to [always] want to have a happy ending or a little lightness. I have certain people around me who are really, really helpful in creating cool ideas and keeping me on track and making sure I picked the right thing. [Writer] Kim Shumway, for instance, was always right there saying “No, no, we have to do it. We have to irradiate. We have to do it. We can’t go soft and let the children escape or some other thing.”

What activates that is that I could credibly see that going either way — Clarke had reason to do it, and reason to not do it. Each of those choices is valid.

Well, I think you have to earn that credibility in an audience. If you know that anybody can die because the show has earned that, you watch the show differently. You see things happening and you say, “No, no. No way are they going to kill Clarke. She’s the lead.” But then you think to yourself, “Hmmm, well, they did kill Finn.” So you never know. Some of the invincibility comes away from the protagonist, which I think is important to make the drama feel real.

But with Clarke, for example, there’s something worse that you can do to a character than kill them.

You can make them live with it.

Exactly. Some shows seem to think that the only bad consequence is an explosion or a death, when really, a character having to continue knowing what she knows — knowing what she did, even for reasons she believed in — can be worse.

Sure. That’s the other side of the coin of the choice to do the dark thing. Whether it is irradiating Mount Weather [or something else], you then have to be honest in the way it affects the characters going forward. You can’t let them off the hook. Raven’s injury from Murphy in season one — it will be with her forever. She’s now disabled. I don’t want to pat myself on the back for this because I’m sure a lot of shows would have done it this way too, but how many times have you watched a show where like suddenly [an injury] is gone? They forgot that that happened.

Someone broke an arm Tuesday, but it’s OK now.

Right. Sometimes you have no choice and sometimes things move so quickly, and I’ll watch a cut or dailies and I’ll be like, “He should have more bruises on his face because he just got beat up the episode before.” Ninety-nine percent of the time, our people in production on set are so awesome with that stuff, and they don’t make any mistakes. They know that’s the way I want it to be — I want it to leave a mark.

So it’s out there that Alycia Debnam-Carey is back in Season 3 as Lexa.

Yeah. It’s been a little tricky. For Alycia, we had to negotiate with AMC at the beginning of the season regarding how many episodes we needed her for.

Are you willing to say how many that is?

I don’t think that’s a good idea. I do think that she has been amazing. And if somebody came to me with the same request for one of our actors, I would do my best to make it work. Especially since this particular character preceded [her role on] “Fear the Walking Dead.” That’s always a concern when you have an actor in your show that is popping — that someone else is going to grab them and make them a series regular if you don’t. That’s kind of what happened in this case. You know we can’t compete on some level with the cache of a franchise like that, with the numbers.

Clarke and Lexa is something that is obviously huge to parts of the fandom of “The 100.” And of course, I understand why at the start of season three, Clarke was not in a place where she could really think about Lexa in a romantic way.

They were on a break.

A major break. In “Wanheda: Part One,” you show Clarke sleeping with Niylah, the woman from the trading post. Did it ever give you pause to do that, given how many Clexa fans are out there?

Not really. I found some of the internet discussion interesting, in that people questioned whether Clarke was in fact bisexual, because I suppose to some it seemed that Lexa instigated [their kiss]. I knew Clarke was on this walkabout in season three, running away from herself and hiding from what she has done, hiding psychologically from herself. Changing her appearance, because people recognized her when she would blow into an outpost or wherever it may be. And she was probably [having sex] and drinking her way across the post-apocalyptic earth, to try to escape. That was escapist sex in that first episode. I knew that was going to happen. At first, I didn’t know whether it was going to be a male or a female partner. But it did become important to make it a female partner, because I felt like it needed it to be clear that she is bisexual. I usually don’t make decisions based on that. But I didn’t want there to be any doubt about it.

Ryan McGee and I discussed the return of “The 100,” along with “The X-Files,” “The Magicians,” “DC’s Legends of Tomorrow” and several other shows, in the most recent Talking TV podcast, which is here and on iTunes.

“The 100” airs Thursdays at 9 p.m. on The CW.