For Mike Hill and Guillermo del Toro, it all started with Frankenstein.

Years ago, Hill — a sculptor and special effects artist — was exhibiting his works at a convention in Burbank. Del Toro saw some of Hill’s monstrous creations on display and was so impressed that he decided to get in touch, tracking down Hill’s contact info from an obscure model kit forum. “I don’t know how he found me from some 20-year-old website,” says Hill, who describes del Toro’s investigation as “very Columbo-esque” work. “But he wrote to me, told me who he was, and asked to commission something.”

That first commission turned out to be a sculpture of Boris Karloff having his makeup applied for the iconic 1931 version of Frankenstein, and it would go on to be displayed in the director’s famous Bleak House. “Immediately it was Frankenstein,” Hill says, “our very first job together.”

From there, a fruitful relationship blossomed; Hill went on to design creatures for films like Nightmare Alley and The Shape of Water, and the Netflix anthology Cabinet of Curiosities. But when word came out that del Toro was working on his own long-awaited version of Frankenstein, Hill’s phone remained curiously silent. “I was fretting because I knew he was going to do Frankenstein and hadn’t been in touch with me,” Hill tells me. “It was driving me bonkers.” But del Toro hadn’t forgotten about his partner — in fact, it turns out Hill was vital for the project.

“Guillermo invited me for breakfast and he said: ‘Listen, we’re doing Frankenstein. If you’re not doing it, then I’m not doing it, so it depends on you right now. Eat your eggs and tell me at the end of it if we’re doing the movie.’”

Naturally, Hill said yes.

That version of Frankenstein had a brief run in theaters and will be streaming on Netflix on November 7th. And it was particularly challenging for Hill given how ubiquitous Frankenstein’s creature is. Karloff’s interpretation from Frankenstein in 1931, designed by legendary Universal makeup artist Jack Pierce, is an indelible part of pop culture, and since then there have been hundreds of variations across stage and screen. “It was very difficult trying to come up with something that no one had ever seen,” Hill says.

The design process was a collaborative one between the director and artist. Del Toro didn’t provide explicit instructions, but instead explained what he didn’t want. The creature shouldn’t be hideous, for example, which meant no heavy, ugly stitching. From there Hill created a few options, and spent some time researching 18th-century surgery techniques, before hitting on the final version. “I just wanted to make him of the period, like he was built in the 1800s,” Hill says. “I wanted it to look like a human being had meticulously done this to him.”

This iteration of the creature is tall and lean, with scars covering his entire body to create an almost geometric pattern. This fits with the story of the film, which really digs into the pseudoscientific process that Victor Frankenstein goes through to build this creature and eventually bring him to life. And that contrast between beauty and horror is a key part of the character, according to Hill. “There’s a certain beauty that Victor was striving for,” he says. “He tried to make a beautiful glass window, it just ended up stained and broken.”

In those early stages, Hill had little to go on. There was no script, nor was anyone cast as the creature. Later, he spent eight months designing prosthetics for an actor who eventually left the project due to a conflict. At that point, del Toro sent Hill a list of potential actors he was considering to take over, and one in particular stood out: Jacob Elordi, who eventually took on the role.

Hill cites “his demeanor, his gangliness, his limbs, his doe-like eyes,” as the reasons Elordi was so perfect as the creature. It helps that the Euphoria star is a towering 6-foot-5 and, according to Hill, has the kind of face that makeup artists dream about. “Jacob’s bone structure made things a lot easier,” he says. “He has this very strong jaw, this very strong chin. Speaking as a prosthetics artist, chins are a pain in the ass.” The final version of the design involved 42 different prosthetics pieces, and when Elordi had to wear the full-body kit, it required around 10 hours in the makeup chair.

One of the most important parts of the final design is how it’s able to evolve over the course of the movie. Initially, the creature is bald and nearly naked, signaling his childlike innocence. But after being abandoned by his creator, he takes on a harder look, eventually growing out his hair and wearing a long cloak. Elordi’s demeanor changes as well; he mostly cowers early on, before being turned into something much more menacing and terrifying. From a design standpoint, all that really changes is the hair and wardrobe; and yet, the transformation is dramatic.

In the end, Frankenstein proved to be an ideal collaboration for Hill and del Toro. The artist tells me that he’s been making monsters since he was a kid, scooping up mud from a nearby riverbank to sculpt them with, and from those early days Mary Shelley’s story was a guiding influence. He went on to create multiple versions of the creature as a professional artist, and is currently working on a short film based on a decade-old sculpture. Just like del Toro, the idea of tackling Frankenstein in his own way was a longtime goal. So while it may have involved a bit of stress waiting for del Toro’s call, it was ultimately worth it.

“I always dreamed that he would make it,” Hill says.