Cersei Lannister (Lena Headey) has been one of the most formidable characters in “Game of Thrones” since its very first episode — a calculating and ruthless political operator who has outmaneuvered the many men her orbit who have underestimated her because of her gender.

But season five saw Cersei’s fortunes begin to change, after her youngest child, Tommen (‎Dean-Charles Chapman), ascended to the Iron Throne and married the equally cunning Margaery Tyrell (Natalie Dormer), a woman whose ambitions were just as lofty as Cersei’s and whose strategy was to beguile instead of intimidate. In Margaery, Cersei may have met her match, and after succeeding in getting her rival and Margaery’s brother Loras (Finn Jones) imprisoned by the Faith Militant, Cersei fell into her own trap. She inadvertently gave the High Sparrow (Jonathan Pryce) and his followers the power to imprison her for her incestuous relationship with her cousin Lancel (Eugene Simon) — not to mention the persistent rumors about her affair with her brother, Jaime (Nikolaj Coster-Waldau).

In Sunday’s eventful season five finale (SPOILER ALERT), a desperate Cersei finally felt compelled to admit to her affair with Lancel in order to escape captivity, leading to a harrowing “penance walk” through the streets of King’s Landing, stripped naked and shorn of her hair while the impoverished residents of Flea Bottom hurled insults, excrement and rotten vegetables at her. It was Cersei Lannister as we’ve never seen her before — humbled, exposed and vulnerable.

After earning an Emmy nomination for her powerful performance last season, Headey is once again an awards contender for Cersei’s stunning fall from power in season five, and Variety spoke to the actress about her character’s unexpected trajectory and where Cersei will go from here… After all, a Lannister always pays their debts.

What was your reaction upon reading the script for the finale?

I knew this was the season that the walk would happen. When I first met Dan [Weiss] and David [Benioff], we talked about it — this was the end to a very painful yet important journey for Cersei. So, I was really excited to take this character of privilege and denial and break her down a little… although I don’t think Cersei can ever truly be broken.

What stands out most to you about filming the confession scene with Jonathan Pryce?

I loved doing that scene. I love when you get a good long David and Dan scene between two driven characters. It was Cersei showing real vulnerability and desperation and yet lying, all at the same time, which is one of Cersei’s natural gifts.

How long did the scene take to film?

It actually wasn’t that long. No complicated camera work. Just focus and finding different ways to play with it all. Fun.

What was the most challenging aspect?

Spiders on the roof that were not small. I don’t like spiders.

What was the most satisfying aspect?

Feeling that you did the words justice. That you took them and played with them. Getting lost in it all for a moment. Showing a different side to a character.

Did director David Nutter give you any useful advice?

I’ve known David Nutter for a long time. We have a shorthand. He has a twisted sense of humor and he’s not afraid to tell you when something isn’t working, which I appreciate.

What was the atmosphere like on set during your scenes?

We have such a stellar crew. It’s our sixth year together. We laugh a lot. When cameras are on we’re all pretty focused and respectful of each other.

Any memorable moments from filming this episode that still stick out to you?

Just that location — Shane’s Castle outside of Belfast. It’s ravaged and filthy and of course looks amazing. But as I said, it’s full of massive spiders that like to drop unexpectedly from the stone ceiling. So trying to retain some kind of regal physicality whilst cowering inside, that’s memorable for the wrong reasons.

Why is Cersei so reluctant to admit to her relationship with Jaime, but not Lancel?

Because of her children. Most folk know by now her kids are her life. She said in season two I think, if it wasn’t for her children she would have thrown herself from the highest window. To admit that relationship, to admit her children are born of incest, even Cersei doesn’t have a way out of that truth.

It’s very rare to see Cersei vulnerable — how did it feel to lay her emotions bare to the High Sparrow when she begs to see Tommen?

It was a great moment to play. Cersei is such a good liar. So for her to be truly laid bare was a new path. I was missing my own son at the time we shot this and so it wasn’t hard to find this truth.

What is going through her mind during her confession?

She just wants to get out, by whatever means. She wants to see her son, to see that he’s OK. To make sure Margaery is still locked up. To make sure everything is as she intended. To see if Jaime has Myrcella.

The most striking part of Cersei’s walk — at least in the book — is that she tries to maintain her pride and power throughout, refusing to let it break her. Did you feel that it was important to convey that aspect of the scene? Was it something that David and Dan made clear in the script?

Yes it was clear in the script. She can see the Red Keep in the distance, she knows her son is there. She doesn’t care about anyone else at that moment. She’s stripped and her hair is shorn and she has to walk through miles of people who despise her, who are hungry and homeless because of her, but she doesn’t care. I said to Nutter, “she just has to walk, no head turning, no eye contact, just keep moving.” When she gets to the gates of the Red Keep with fewer eyes on her then she can break a little. She has a goal, a focus and that’s what keeps her moving forward, she doesn’t once let go of the fact that she will be able to hold her son at the end of this. To make sure he is safe.

Where does Cersei go from here?

When she walks through the gates, the men standing and staring, people she has known for years make no effort to comfort her. Only Qyburn and his creation come to her rescue. She has been humiliated on an epic scale. But she’s a survivor. Cersei moves on quickly. Her thoughts of vengeance are already forming. In fact what kept her spirits up in the cell were thoughts of how she can hurt those who hurt her.

Have her experiences this season changed her irrevocably, for better or worse?

They have changed her, yes. This is where her descent into true madness begins. She has her two remaining children who will offer her some grasp at sanity. She has not given up on ideas of power and revenge. She has a mad scientist by her side now. Someone who isn’t afraid to speak honestly to her but is also in her debt. Cersei won’t forgive or forget so I think some interesting moments lay ahead.

Does she worry Tommen will look at her differently following her ordeal?

I don’t believe she does feel that. They are close. He’s a good, kind boy and she believes that she can make it all better for him now she’s free. We’ll have to see.

Where does she stand with the Tyrells, especially Margaery, going forward?

Well I think we can say that relationship is truly shattered. Though I’d love a showdown with Olenna and Cersei. And, let’s be honest she’d happily murder Margaery with her own hands.

Is she concerned about what Jaime will think when he learns of her walk?

No. Her concern is her daughter. Jaime and Cersei’s relationship is damaged beyond repair. She doesn’t care what he thinks. There is love there for sure but it’s now severely warped.

This season has allowed you to explore many different facets of Cersei — was there anything you found surprising or unexpected about her evolution this year?

Not really surprising. She’s always been someone who holds onto what she wants to be the truth. Her ability to lie and live in denial is one of her greatest strengths and biggest weaknesses. Her belief in herself is so great, at least whilst her children live and breathe. We were always headed for this moment for her and now this is where it gets really interesting. This is where the unexpected begins. I think. I hope.

What do you most admire about Cersei, and what do you think is her biggest flaw?

Her survival skills. Her ability to navigate amongst men who don’t believe in her. Her devotion to her children. Her flaw is her inability to listen to the few who really do care about her. She doesn’t think she’s worth that investment.

What is one piece of advice you’d give to Cersei?

Oh god. Maybe slow down on the wine. Move to the countryside and raise your kids. Live the simple life. That’s not going to happen so, watch your back Cersei. Seriously.

What do you most appreciate about David and Dan’s writing?

It’s exciting, getting the scripts, because there’s always one or two big scenes that you read and they are full of gifts: emotional, motivational, surprising moments. David and Dan are a rarity. They remain available and collaborative. They’re smart and funny and genuinely care about their actors. Because we’re on our sixth season, they know us all and they embrace our strengths as actors. Not to say they don’t push us, they do, they enjoy challenging us and for that I am deeply appreciative.