*Spoilers for all season four, volume one episodes below*

"I knew nothing."

One of the newest additions to the Netflix series is Jamie Campbell Bower, who first appears in the latter half of 'Stranger Things' season four as Peter Ballard, a friendly orderly in the throwback Hawkins experimental facility where Eleven (Millie Bobby Brown) must revisit in order to get her memories (and more importantly, her powers) back.

However, by the end of episode seven, which serves as the mid-way point of the season, we've learned a great deal more about Peter which changes the story quite horrifyingly.

We broke down that super-long episode seven in great detail (here), but to summarise: Peter is actually the young boy once known as Henry Creel, who was then known as "001" by "Papa"/Dr. Brenner (Matthew Modine), who eventually turned into the big bad of the season, Vecna.

In an interview with Entertainment Weekly, Jamie Campbell Bower broke down his 'Stranger Things' character in great detail, revealing that he knew "nothing" about the role before signing up, plus how pretty much everything of Vecna that we see and hear on screen is actually him (with some added CGI, naturally).

On first getting the starring role in the season, he said: "I knew nothing. They sent me two sets of sides, originally. One was from 'Primal Fear' and the other one was from 'Hellraiser'. Then for the recall, they sent me some dummy sides from the show, at which point there was a little bit more information about the character, but not loads.

"It was mind-blowing. The way I always saw this journey for Henry was: sweet, sweet, sweet, nice, nice, nice, manipulate, manipulate, turn, full-on total resentment, hatred, carnage. [...]

"I have no idea where the name Peter Ballard came from. I can only apologize to fans of the show for being part of such a massive red herring. I remember seeing it and being like, 'Okay, guys. Cheers! That's going to be a tough one if anybody asks me, but I'll just go with the party line'."

33-year-old Jamie Campbell Bower should be familiar to 'Stranger Things' fans for his appearances in a number of other sci-fi/fantasy movies. He played a young Gellert Grindelwald in 'Harry Potter and the Deathly Hallows: Part 1' and 'Fantastic Beasts: The Crimes of Grindelwald', Caius in 'Twilight: Breaking Dawn' and Jace in 'The Mortal Instruments: City of Bones'.

It turns out that most of what we see of Vecna on screen is Campbell Bower in a specially-made suit and prosthetics. He says that "ninety percent" of what we see is practical, and he had to get used to having extremely long hands. He continues: "Yeah, that's me doing the voice under the prosthetics. It's all me. Ninety percent is practical. The only thing that is not practical are the vines moving on the neck. [...]

"The physical element of Vecna came beforehand. I knew I was going to have this incredibly long hand. I would spend hours looking at my hand, imagining my fingers extending further out, and playing with that a lot. There's a certain stillness to him. Everything's very methodical.

"There was another really interesting thing that came as we were filming, too. It came from within. It was like I had to push the energy out of my body so I was really filling the space, presence-wise. I remember walking onto set as they were building Vecna's mind lair and looking at the size of it going, 'Holy f---, this is huge! I really need to own this space 100 percent'. [...]

"There's that Kubrickian stare that I wanted to bring into it, as well."

The actor also revealed that that really is his voice we hear as the creepy, drawn-out drawls as Vecna talks to his victims. He said: "It was funny. I was in ADR for the show a couple of weeks ago and the engineer was like, 'I've got this octave [voice distorter] for you'. I was like, 'Oh no, we don't use that. It's all me'. He was like, 'Yeah, whatever. Go on'. And so I did it and he was like, 'Right. Yep. I've cancelled the octave of that. It's off now'.

"But it was hard as we were filming. Because the suit comes over the ears and the ear holes are very, very tiny, to be able to fully hear myself was quite difficult at the time. I was feeling it, but there's always that wing and a prayer where you're going, 'I think it's good. I hope this is coming across well'."

And finally, what's in store for viewers as we await the bumper two-episode finale? Thankfully, he's not giving anything away. He said: "I'm going to toe the party line here. It gets bigger. If you thought that it was as big as it could get, it's not. It goes further, visually, story-wise, and emotionally for all the characters. It really is quite an explosive climax, let's say. I know lots of people have used the word explosive and scope and scale, but I do mean that. It goes a lot further and we get to know more as well. We learn a lot more as an audience in these final two episodes, as well."

'Stranger Things' season four, volume one is available on Netflix now. Volume two arrives on July 1.

Read the full interview over at Entertainment Weekly.