This article contains spoilers for series four of Stranger Things
Jamie Campbell Bower, who plays the monstrous Vecna in the latest season of Stranger Things, has arguably suffered for his art after enduring eight hours of make-up a day to become the Netflix show's supernatural serial killer.
He's pretty relaxed about it, though, saying he took regular breaks throughout the painstaking process.
"I'll be honest, I'm a smoker. So we went into this great flow, where we realised we could maybe take about a five-minute break every hour or so.
"I'd step outside, grab a bit of air."
Coated in lubricant
Fans of the hugely popular show, which first appeared in 2016, are preparing to see what happens to the inhabitants of Hawkins when it returns on Friday.
Campbell Bower is obviously key to the storyline, and tells the BBC it was an "absolute pleasure, an honour" to work with Barrie Gower, who created the show's creature prosthetics.
Gower also created prosthetics for Game of Thrones - including the terrifying Night King - and radiation burns on TV drama Chernobyl.
Vanity Fair produced a YouTube video about Vecna's make-up process, which Gower explained ended with a 15-minute session coating the actor in lubricant to make him look "glossy". It was a bit of a surprise for anyone who shook hands with him on set.
As volume one of season four ended, fans learned that the Upside Down and Vecna were the aftermath of a huge fight between the psychokinetic powers of Campbell Bower's pre-Vecna character and Millie Bobby Brown's Eleven.
Campbell Bower says he had to ooze Vecna's evil energy through the 25 prosthetics, which were glued to his skin.
"I came to the understanding that my skin had to be another layer above itself. The energy has to push through another level of clothes, so that it was exuding from the costume itself."
He says some scenes were "terrifying" because he realised he had to "fill this stage with my presence... it was crazy, just crazy".
So how did he prepare to be so utterly terrifying?
"I did a few things," he explains. "I had a mood board that I started making quite early on in the process. So I always had that with me on set and where I was living, and it grew over time."
He added pictures of characters on the show he would be interacting with, scribbling on their images with a red pen.
"Meditation was also a big thing. Clearing out my own space, allowing this fury and resentment to come through, was very interesting for me," he explains.
"I spent quite a bit of time kind of on my own, walking around saying the same thing over and over again, staring into the eyes of whoever was next on the mood board."
As well as focusing on the role mentally, he also ensured everything he looked at was connected with his character - even his phone background, which he changed to a burning house.
"For those of you who have seen the first volume of season four, obviously there's a story there with his father Victor," he says. "So I just made sure that everything I was ingesting was of relevance.
"I threw myself into it - if you don't commit yourself 100% to something, your chance of success - feeling fulfilled and a sense of achievement - is significantly reduced.
"I'm only here once, so why not?"
Campbell Bower is softly spoken, and nothing like the growling, sadistic Vecna. So what was it like to scare the life out of his castmates?
He lets a laugh escape and says: "I'll be honest with you, it was really fun. As an actor, you're sometimes fortunate enough to be given a position of power within scenes.
"It taps into a very interesting side of the human psyche, which is, 'I'm in charge now'.
"It's quite an enjoyable moment to go through - obviously there were times where I felt bad for my fellow team members. So we'd make sure they knew that it was me inside there, a gentle touch of an arm or just to look in their eye to say, 'It's me by the way, it's OK'.
"I think it put quite a few people at rest, but some of the crew were terrified, particularly when we first started working.
"I was skulking round a corner and bumped into a crew member, and there was this scream from the side of the stage, and I chuckled to myself. That was fun!"
The arrival of Vecna has coincided with the show propelling Kate Bush's hypnotic hit Running Up That Hill to the top of the UK singles chart, 37 years after its original release.
The song features as a recurring motif, obsessively played by one of the teenage protagonists, Max Mayfield (played by Sadie Sink), as she struggles to come to terms with her brother's death.
In one pivotal scene, Vecna tries to invade Max's mind - but Bush comes to the rescue.
"Her friends realise the best way to get her out of this state is to play music, to remind her of reality," says Campbell Bower. "It's the space she goes to to feel safe and comfortable.
"All of a sudden, the song starts playing and it gives her the strength and the power to overcome that moment, which I think is absolutely beautiful."
He calls the song "ethereal", saying: "I think it's just grabbing at the emotional core of who we are. And that comes from everyone involved in the process - Kate Bush, the team, everyone. It's amazing."
Campbell Bower is also a musician and singer. So what songs would he listen to, to snap himself back to reality?
"Goodness me, it really depends on what sort of mood I want to be in," he smiles.
"For me, I tend to use music to emphasise a feeling that I'm having on the inside, or to draw power to within myself.
"When I was preparing for this show, it just so happened that at the same time I really got into [the album] Pornography by The Cure. That record makes me feel very grounded, brings me back down to earth."
Away from Stranger Things, he says "bands like Blink 182 were a vibe for me", but adds: "I love everything. I absolutely adore everything."
He adds that for the finale of series four, he listened to "dark, heavy music that would increase the heart rate".
"I think often we're not very conscious of the fact that music has such an impact on the choices we make. There's there's a specific reason that supermarkets play some music - you know, it forces you into a state like, 'I'm gonna buy this now'.
"So I'm always very interested in that, too."
He also talks about the scale of Stranger Things, and "the talent and the intelligence and the genius of the writing and the crew".
"It's a total blessing to be around," he says.
"I consider myself lucky. I pinch myself often, and it's just a really great group of people who really care about making something beautiful. What more can you ask for?"
Volume two of season four of Stranger Things is on Netflix from Friday, 1 July.