How do you design a new species? That was the challenge facing the crew behind ABC's "Marvel's Agents of S.H.I.E.L.D." this season when they set out to reveal the Inhumans -- superpowered individuals, some of whom look like us; and some who most definitely don't. And it all started with one recurring character: Raina, played by Ruth Negga.

Actually, to be more accurate, it started with a phone call and a vague idea.

"It was more of a metaphorical concept of her expecting she’d become a flower, but instead becoming thorns," Glenn Hetrick of Optic Nerve Studios -- a.k.a., the guy in charge of creating Raina's look, told MTV News over the phone. "You start with a loose idea because of the efficacy required by the screen writing... Creatures or effects are relegated to just one or two lines."

On "S.H.I.E.L.D.," Raina has spent the past two seasons searching to become something more than human. Initially, she was just an enigmatic villain in a flower dress. But over time, as she became more integrated into the overall mystery of season two, it was revealed she was after something in particular.

That particular thing turned out to be Terrigen Crystals, a macguffin that releases a mist killing regular humans, and turning humans with dormant Inhuman genes into superhumans. For Skye (Chloe Bennet) that meant keeping her good looks and gaining out of control earthquake powers. For Raina, it meant something else entirely.

"[Raina] was the woman who had gotten everything she ever wanted and was super smooth and manipulative," Jeff Bell Executive Producer said on a separate phone call with Jed Whedon, one of the show's head writers. "And what would happen if she got what she wanted but instead of becoming a beautiful flower, she became a monster?"

A lot of time was spent in the writer's room debating Raina's look -- "does she have a tail? does she have a nose?" posited Whedon -- before one simple suggestion was brought up.

"I believe it was [writer] Drew Greenberg who said, 'what if you gave her thorns?' and everybody kind of went, 'huh.' " Whedon continued.

Other than the thorns, and Raina's emotional arc, there was one other idea the writing team went to Hetrick with: you had to be able to see Negga's eyes.

"Ruth Negga has amazingly expressive eyes and eyebrows," Bell said. "And she gets so much of who Raina is through the eyes. We wanted her to still be able to communicate, we still wanted you to feel her expressions through all of [the makeup]."

With that in mind, Hetrick and his team pulled on a few surprising sources of inspiration, including the cult-classic Cliver Barker film "Nightbreed." Specifically the character Shuna Sassi, played on screen by Christine McCorkindale.

"She's a creature covered in porcupine quills and that image is so strong -- it creates such a striking silhouette -- so it’s always stuck with me," Hetrick recalled. "I have to be honest, I’ve always kind of wanted to do my version of my makeup that looks like that."

One point of reference Raina doesn't have? The comics. Unlike Skye, who is pulled off the page (in the comic "Secret Warriors," she's the superhuman S.H.I.E.L.D. agent called Quake), Raina is an entirely original creation.

"She’s very much her own thing, the way we designed her nose and the mandibular arch, the muscle," Hetrick said. "We tried to make her feel like the first real Inhuman -- but there’s not specific reference to the existing characters."

Hetrick then went to fellow designer Neville Page (a judge on the SyFy show "Face Off"), who created some Photoshop takes on a possible look for Raina's Inhuman evolution. Hetrick's main directive? To give Raina's face a level of symmetry to the design, hence the opposing swirls you see on either side of her nose.

From there, Hetrick and his team (including Michael Obrian, Erin Draney, Ken Culver, Danielle Noe, Ozzy Alvarez and Rocky Faulkner) had less than two weeks -- normally a three to four month makeup process -- before Negga would be filmed in her Inhuman guise. To speed things along, Hetrick and company sculpted in clay, allowing the producers to instantly see what Raina might look like post-transformation.

Based on comments, Hetrick and company were able to break down the prosthetics to their component parts, while simultaneously prepping the makeup Negga would need to make everything look smooth.

And the entire time, they were fighting the clock. "I was painting the stuff the night before the test," Hetrick recalled, "and the test was two days before she shot. So it all happened so quickly."

Once Whedon and fellow head-writer Maurissa Tancharoen saw the makeup though, Hetrick knew they had a winner. And when Negga wore the prosthetics on camera, it only confirmed it: this was the design they were hoping for all along.

And the whole time, one thing that didn't even remotely enter the conversation? What Raina's actual power would be. Which, when you think of the whole of superhero and supervillain-dom, is kind of surprising.

Spider-Man has a design like a spider web. Captain America looks like a flag. And Hulk is, well... You know. But with Raina, it always came back to her emotional arc.

"We knew we wanted her to talk about the concept that your power sometimes comes with a price," Whedon said, "and that it's buried inside you... You could present as something horrifying, but inside, you’re something beautiful. That’s sort of our goal with the Inhumans, just to show that people want to be accepted even though they’re different."

In fact, the team knew potentially what her power was -- spoiler, it turns out to be clairvoyance, a bit of an in-joke if you know Raina's season one arc -- but left it open, just in case.

"We had the idea of what her power was going to be," Whedon continued. "Not that it couldn’t have changed, but we didn’t feel like it would be thorn related."

There was an extra added level of pressure to Hetrick's design, too: he wasn't just debuting a new look for the character Raina, she's the first of a new race of Inhumans -- characters that won't just be showing up on "Agents of S.H.I.E.L.D.," but also on-screen in 2019, in a big-screen "Inhumans" movie.

Unlike previous movie/TV tie-ins, such as the ones following "Captain America: The Winter Soldier" or "Avengers: Age of Ultron," where the movie plotlines dictated what happened on "S.H.I.E.L.D.," here the TV show is blazing a new path.

And though the producers initially didn't tell Hetrick what Raina was supposed to be, he knew almost instantly they were asking him to design the first Inhuman... And he couldn't have been more excited.

"I went in there and we started talking, and I got it," Hetrick said. "It was, like, I can’t even explain the experience because I have seen everything [Marvel has] put out going back to, you know, old 'Punisher' movies and even the Dolph Lundgren version of the 'Punisher.' "

Hetrick added that when they finally said out loud that she would be an Inhuman, he was totally overwhelmed, because, "It’s something that I hoped to be a part of for a very long time."

For Whedon and Bell though, there was the pressure not just of introducing Inhumans to the Marvel Cinematic Universe, but as importantly to the show itself.

"One of the risks with makeup," Whedon said, "unless you approach it right and you feel like you have a taste level for where you want it, it sometimes just plays as goofy."

Though "S.H.I.E.L.D." exists in the same universe as Asgard, rampaging green monsters, and alien Chitauri armies, the show has taken a ground-level view of that, focusing instead on character's emotional arcs.

"This was the visual representation of a human being that has transformed," Whedon continued, "and so we did feel a responsibility. Not to necessarily set the tone for all Inhumans, but more just not blow it in our first attempt!"

Bell agreed, citing the "X-Men" as a model, noting that while the comic book versions of those characters go wild, on screen they're decidedly more human looking.

"Every now and then you’re gonna have a Mystique," Bell said, referencing Jennifer Lawrence's character from the movies, "or you’re gonna have someone who looks a little bit different -- and so we wanted a mix. We didn’t want it to be all just beautiful people running around, but also we're a network show, not a SyFy or other niche show... So we needed to exist in a world that was accessible to a grown audience."

Hetrick agreed, referencing other productions he's worked on like the "Hunger Games" movies, saying, "That was the goal –- to make her feel fantastical and beautiful, make her feel like an Inhuman... But not so ridiculous or wildly colored that you can’t believe it exists. And hopefully we succeeded. And that will be the goal with all of the designs that we do in the future."

Those future designs may come with challenges of their own. Even after all of the tests on and off set, and the approval of all around, there were still surprises once the cameras started rolling. At first, the idea was that we'd see Raina's evolved character in the shadows, slowly revealed over the course of a few episodes.

To do this, they added a hood to her costume... Which had a kind of hilarious side effect.

"When she would pull it off it made this terrible sound!" Whedon said, laughing. "And so we leaned into that. Every time she pulls up her hair, you’ll notice the sound is really the sound of prickly things being... I don’t even know how to describe it. Some of it you just discover in the moment."

With that in mind, and the season finale hitting on May 12, "S.H.I.E.L.D." is using Raina as the test case for adding more Inhumans -- and superhumans -- in the future.

"As we get deeper in and people get used to it, we might be able to populate the world with more strange things," Whedon said. "But at this point we’re taking it slow."

Check out a few other pieces of concept art from Neville Page, and shots of Negga getting into makeup, below!