"I choose violence."

With those words, heard in the trailer for Sunday's upcoming Game of Thrones, Cersei (Lena Headey) quietly and clearly states that she won't back down from the Faith Militant, who is fronted by her cousin and ex-lover, Lancel Lannister.

"The feeling of the scene that's coming in episode eight is one of a huge fight of power going on between Lancel and Cersei," Eugene Simon, who plays Lancel, tells The Hollywood Reporter. "This is about trying to determine the boundaries of how much power the Faith is now capable of exerting on Cersei, and basically the Crown. There's still a fight to be had. This battle, this war is not won. I think what fans should really keep an eye out for is who did it look like is going to break first: the Faith or the Crown? They will see by the end of that scene that there's still a lot more work to do."

Flanking Cersei are two men: disgraced maester Qyburn (Anton Lesser) and the hulking form of Gregor "The Mountain" Clegane (Hafthor Bjornsson), who was killed by poison after a trial by combat and resurrected by Qyburn's illegal human experiments.

Simon shares what it was like doing the scene. "While we were shooting it, it took about two-and-a-half days to maybe finish it because there was a little bit of stunt work that had to be done and some kind of prosthetic work to properly get across the awfulness that happens in it, which was very fun," he says. "Hafthor is an absolutely enormous human being. He's one of the strongest men in the world, possibly the strongest man in the world. But while shooting it, that guy is wearing 28 kilos, about 58 pounds worth of solid armor. It's seriously heavy stuff for one thing. So he really fits the part as much as looking it."

Read the rest of Simon's conversation with THR for the actor's take on Lancel's opinion of the High Sparrow, his loyalty to the agenda and why the Faith now wear sandals.

Does Lancel believe in the Faith's extreme tactics — the violence and Cersei's humiliating walk of atonement?

I don't think it's something that he necessarily loves. I think it's something that he takes a rather troubled sort of pleasure in, but not in the sense of what we think about retribution. It's much more about justice than say revenge. But he certainly holds contempt and loathing and believes everything that he's doing unquestioningly. He certainly believes all in regard to why they are doing it and why they are going after this important figure because once you cut the head of the fish off, the rest sort of falls into place really. So he's fully aware what he's doing much of it is about this idea of righteousness, this idea of justice, taking back the power from this evil authority that they all see in the Crown.

Now that he's on his path, are there any lingering feelings of shame for what he had done?

Here's the thing: Lancel spends so much of his time thinking about who he used to be. The Lancel you see now is pretty much predicated upon the fact that he tried in every way because he believes so firmly in redoing himself in the name of the gods. He always has to keep a very close eye on and stay away from his former self. And not just in terms of these puritanical ideas of sin, but also he doesn't want to be vulnerable, he doesn't want to be weak, he doesn't want to be exposed. And he doesn't want to have anyone experience what he experienced really. He's willing to go to incredible lengths to do that. I think that he is sort of fully consumed by it.

Does he have any loyalties to his dad Kevan Lannister (Ian Gelder)?

He certainly rejected his household but I don't think that he truly rejected his father. Within the Faith there are laws and traditions that have to be kept. And I think the idea of "honor thy mother, honor thy father" — I don't think that it goes anywhere. There is a creed. Politically he's quite rogue, but in terms of his personal life, I think he does hold some affection for his father in the way someone is supposed to ... I think it's really sad that he's had to say goodbye to his family because there's no real choice, he has to do what he's got to do. He's got a real agenda and a motive now. I think dad has probably left the picture in his mind.

How does Lancel view the Faith's leader, High Sparrow (Jonathan Pryce)?

With a great bit of loyalty and respect. He sees the High Sparrow as this figure of real progress in some ways. He's moving things along, he's moving the ball down the field. Lancel is only too willing to do what he can to part of that. He's very much a hands down on the ground kind of guy. He gets involved. Lancel gets to break into the thick of it. He's not here to mess around. He can be violent. I think having someone give Lancel a direction is appreciated.

What does Lancel think about Margaery (Natalie Dormer) and Tommen's (Dean-Charles Chapman) about-face and support of the Faith?

There is a confidence in the Faith. I think Lancel views the conversions of Tommen and Margaery as very sound. I think Septa Unella (Hannah Waddingham) in the last scene was very confident when Margaery and the Queen of Thorns (Diana Rigg) were talking together. There was an unbreaking smile. The Faith may be overly arrogant in its conviction that it's going to teach you to convert people, but that's to be seen.

Now that you're wearing robes all the time, is that now a comfortable costume for you on set?

Yeah in some ways it was a big relief. The material we wear is very comfy. I saw the other day on Twitter that people were surprised that the Faith is now wearing shoes, they're wearing sort of sandals. The idea was that the Faith Militant wears sandals and the Sparrows don't just because of the nature of the job of the Faith Militant, who need to be more rough and tumble. I rather miss being shoeless. I miss not wearing shoes. Feeling cold stone underneath your feet is a rather pleasurable part of shooting. But I think Lancel for the time being is stuck with sandals, stuck with chains and stuck with a big old metal and wood cudgel to really grit things up.

What is it like to wield that?

It is a pretty intense weapon. When you hold a sword, there is something sort of elegant about swords. But there's something about this cudgel with four little prongs at the end of it that is so sort of brutal, so sort of bludgeoning. It's a quite extraordinary thing to wield it but once you're on set and in character it becomes second nature I guess. It weighs probably 15 pounds, maybe 20. It's a proper bit of kit.

With you turning 24 on June 11, do you see any sort of parallels in your journey and Lancel's, in terms of coming to maturity on the show?

pSo much so. It's one of these lucky coincidences in a career when you're at an age when you're going through a lot of change. When you come back to a character that has offered you to portray them in a very changed way, that's such a feeling that you can identify with. I can identify, not necessarily with his choice, but with Lancel's desire to change. I'm very lucky I got to play him because it showed me how much you're — as an actor when you develop as a person, you tend to develop as a performer as well. Nothing is wasted as a result. Your whole life experience is an opportunity to apply to your work. p

Game of Thrones airs Sundays at 9 p.m. ET/PT on HBO. Stay tuned to THR.com/GameOfThrones for full coverage.