Percy Jackson’s journey to demigod happens both in small steps and leaps and bounds. The Disney+ adaptation of Rick Riordan’s Percy Jackson books has shown how certain moments shape the hero Percy becomes. As the first season of Percy Jackson and the Olympians comes to a dramatic close, it’s easy to look back and identify those moments. Percy takes a literal leap towards his true self after he battles the Chimera inside St. Louis’ iconic Gateway Arch. A powerful creature in Greek mythology, the Chimera is a formidable foe for even the most skilled warrior. Unfortunately for Percy, he is not a skilled warrior (not yet, anyway). However, he doesn’t hesitate to confront the beast and save others. We went behind the scenes of the Chimera fight to see how the creature came to life with Percy Jackson executive producers Jon Steinberg and Dan Shotz.

Nerdist: I revisited the Chimera scene in the book, and in my memory, it was much longer than a few pages. How do you approach adapting a brief and pivotal scene like that for the screen?

Jon Steinberg: That story went through a few iterations. In a book you can really slow down the experience of what might only be a short interaction and it starts to feel like a huge experience. On screen, it’s really hard to walk into a room, find this thing, and then walk out and not have it feel like you really wish you got to spend more time.

That was one of the episodes where it was an interesting conversation to have with Rick and Becky [Riordan] about: how comfortable are you to really take this event and think about it in the context of this story differently? Is it not just something we stumble on, but is it something that’s really wired into the moment we’re having in this adventure and gives us more room to breathe? And to their credit, they were really open to it. They felt all of the room there was to move and let it breathe and the things we stood to gain from having that creature be a little more of a character herself.

Dan Shotz: And globally, I mean this story is about parents and children and families. Echidna is barely in the book, and I think there was just so much. How can you not dive into the mother of all monsters and then her creature that she has trained from birth to take down demigods? So, there was so much to mine there. When you’re doing a series like this, these are those opportunities to dig and give them a really detailed story.

Percy Jackson holds Riptide the sword up to fight the Chimera on the Gateway Arch

Let’s talk about the design. The creature is streamlined here. The Chimera could easily come across as a hodgepodge of animal bits. What was the iteration process like to make the Chimera a beautifully terrifying creature?

Steinberg: There were a few different conversations that were happening with each one of these creatures simultaneously. The easiest one to explain was looking at the first 10 things that pop up on an image search when you search for it and knowing that’s not it. Whatever it’s been before can’t quite be the answer. Another conversation was about trying to go back to the bedrock of mythology. What is it in the canon? In the tradition of it, she frequently has multiple heads. We liked the idea of exposing her to evolution, I guess, and forcing that creature to incorporate all of those different ideas into one thing that looked like it was sleek and could move from here to there without falling over under the weight of all three heads.

This is what the concept art team and MPC team came up with. It’s got enough parts of a lion that when it’s moving, it feels a little familiar but not too much. Trying to break it, and then put it apart, and put it back together in a way that feels interesting was the exercise.

Shotz: It was fun for MPC and our team, our VFX team, to figure out how that thing moved when it had—its front paws are lion paws. Its back hooves are goat hooves. As we started to blend all of these creatures together, animals and creatures together, it started finding this beautiful form. And then you run with it because it’s like, wait, it’s doing all of these things and I’ve never seen it before. And it also needs to have fire come flying out of its mouth.

I imagine with those various parts that going to the real world is a reference point. Lots of studying wildlife photography and videos?

Steinberg: We all looked at a lot of lions on YouTube.

Like, our meeting today is an hour of lion videos.

Shotz: You joke, but it definitely happens. When we were sending early concept work, it was literally cutting to shots of, okay, when they move forward, the lion opens its mouth this much and you’re really doing it to that level of detail because that’s the only way to make it look real.

An important part of this battle is the location. Gateway Arch is obviously a well-known monument, so what was it like re-creating that?

Shotz: I’ll say we had to take over one of the largest stages in Vancouver to build that. That set was massive. We also had to build it up so that we could have Percy drop from it, so it had to be elevated. It was a really complicated set. It also needed to catch on fire. We needed all these different elements to make that set piece work.

But one of the things—this is Jon’s fix—was we wanted it to be accurate. So when we looked at it’s like, “Oh, wait a minute.” Everybody always assumed the Mississippi River is right underneath it, but it’s not. It’s actually a good distance. So when we have to drop him, you’re dropping him to the ground. But in the story, we have to get him to the river. Jon gets all that credit because it was a really tricky thing to figure out how to make sense of that. But we wanted it to be all completely accurate. And we went to St. Louis. We scanned everything, the environment, everything around it, the Arch, where the museum is, where the city hall is. All of that is built from scans from actually in St. Louis.

The Percy Jackson and the Olympians season one finale arrives today on Disney+.