Don’t let her immaculate blond tresses and silk gowns fool you: hell hath no fury like a Cersei scorned. As Game of Thrones’ vitriolic and vindictive Lannister daughter, British actress Lena Headey bares her fangs like a female Fassbender, making life miserable for all those around her—particularly her imp little brother Tyrion, whom she blames for killing their mother during childbirth.

“A disease doesn’t decide to kill you—all the same you cut it out before it does,” she tells her brotherlover Jaime during the show’s Season 4 finale. “What do you decide? What do you choose? I choose you.”

“Those are words,” he replies.

“Yes. Like the ones I just told to Father,” says Cersei. “I told him about us. I told him I won’t marry Loras Tyrell. I told him I’m staying right here with Tommen…with you.” She adds, “I love my brother.” And before you can say “incest,” Jaime’s thrown her on a table and the two blood relatives are engaging in some very forbidden lovemaking.

With the Dick Cheney of Westeros, Tywin, out of the picture, the dirt road is clear for Cersei to wreak havoc on the poor Westerosi next season. After all, her barely-pubescent son, Tommen, has ascended to the throne in the wake of Joffrey’s poisoning, and Cersei will no doubt be his own personal Eleanor Iselin.

In an in-depth discussion with The Daily Beast, Headey opened up about her character’s finale reveal, what to expect from Cersei next season, and why the controversial rape scene with Jaime was anything but.

The finale was huge for your character. We see her finally confess to Tywin that she’s in love with her brother, Jaime, and that his legacy is screwed.

I’ve known Charles [Dance] for a long, long time, and he’s pretty formidable. He’s a pussycat off-screen, but he’s ferocious as Tywin. There’s always that strange feeling when you know someone and you’ve spent a lot of time together, and a part of you is thinking, “Shit, this is it. It’s the last time I’m going to get to look in your eyes and do what we do.” It’s kind of weird. But I love that Cersei has that moment of, “Oh, fuck it. My kid’s fucking dead and you’re a shit, so I’m going to tell you how it is.”

Cersei, for all her ruthless scheming, has gotten a really raw deal. She’s constantly diminished by Tywin and treated like a second-class citizen.

He is, without a doubt, the shittest Dad in the world. All she’s wanted to do is sit with him and have him tell her she’s doing great, and he loves her, but she’s given up on that. As a child, you never stop wanting to be validated by your parents—especially with a daughter to a father—and that’s why she has problems with her brothers, because she thinks, “If I were a guy, this would be easier.” But she has a lot to contend with, Cersei.

There was a lot of backlash to the rape scene between Jaime and Cersei in Episode 3 following Joffrey’s death. A lot of people viewed it as rape, but the show didn’t treat it as such, because the scene that follows between them is pretty casual and sees her just calling Jaime “Lord Commander” and dismissing him.

I was kind of shocked by the reaction, actually, because the show is full of crimes against humanity. I found that scene really tough to watch, but I like that—I like my mind being challenged, even if it’s set in this world of Westeros—but the Jaime/Cersei moment, we discussed it and with people losing people that they love, and mothers losing their children, she’s in deep loss and Jaime returns and she loves him, but at the same time she doesn’t want to be near him, but they have all this history and she wanted him. She wanted him. She’s saying “no” for many reasons. She’s saying “no” because of the fucking pain of her loss—she can’t bear what she’s feeling. She was saying, “No, no… not here,” but a lot of stuff was about how, right in that moment, she couldn’t bear to feel what she was feeling and wanted him to take some of that away.

Cersei’s relationship with Jaime has gone through so many twists and turns. When he first returns with his golden hand, she views him as slightly pathetic. He’s no longer the “Kingslayer” she knew and loved but deformed. Then, in the finale, she professes her love for him.

She comes back and she’s a bit like, “Ugh… I don’t know,” and then when he shows interest in Tyrion, she begins to feel that Jaime recognizes something in her that he doesn’t necessarily want to fight for anymore. He says, “Why have the Gods made me love a hateful woman” over the body of their dead son. He’s never said anything like that to her before, and he also stands up to her on Sansa. She’s a kid, Cersei. She doesn’t want the toy unless somebody else wants it, and I think that’s how she is with Jaime. So right now she’s manipulating him, and I don’t know how long that’s going to last but I think he’s had a big change of self.

In addition to that Jamie/Cersei scene, there have been some think pieces surfacing of late that are very critical of all the rape and violence on Game of Thrones. I’m curious what your thoughts are on it.

I don’t know. It is what it is. It’s a world of mammoths, giants, and brothers fucking sisters. I think people can enjoy it because it’s not based in reality. If it was based in contemporary times, people would feel guilty thinking, “This is great!” but with this backdrop, you can lose yourself a little bit.

You’re great at playing this pretty sinister character. How do you get into Cersei mode? Do you have a ritual for transitioning to the dark side?

[Laughs] No. I don’t think she’s particularly dark! I think she’s a survivor and holds onto a reality that she’s created, and it’s very small because it’s full of denial for her, so next season it all starts to fall apart. But the process of going in in the morning and getting the corsets and wigs done and walking onto sets like that really helps, and being an actor and having belief in what you do is the biggest commitment I have in my life besides being a parent.

You mentioned that “it all starts to fall apart” for Cersei next season, but she’s also in a position of great power now that Tywin’s gone. As Tommen’s mother/adviser, she’s essentially second to the throne.

Also she’s lost Joffrey and that was a prophecy when she was small and her ability to live in fantasy is getting smaller. She’s also fearful because Margaery is getting very close to Tommen and she really doesn’t like her very much. I don’t know how they’re going to write her reaction to Tywin’s death, but I’m sure there’s going to be some sort of celebration for her in it. But Tywin’s also given her the knowledge that the Lannisters are pretty much broke, so I think she’s overwhelmed with it all.

In the books, Cersei gets very down in the dumps, starts putting on weight, and hits the bottle hard.

I love that! I think the more broken the better. Cersei’s built where you meet her as this woman who seems to have it all under control—her head’s very nice and she’s well-dressed—and underneath it’s a whirling mess. So we really get to see what’s underneath that façade as the seasons go on, and I think next season is going to be particularly brutal for her.

You said you don’t think Cersei’s particularly dark, but her hatred of Tyrion is pretty evil. When the Red Viper describes how she treated baby Tyrion…thank God they didn’t show that in flashback.

There’s time! There’s time! [Laughs]

Oh goodness, I hope not. But she hates Tyrion so much for “killing” their mother that it’s really colored her outlook on things. Do you think she even believes he poisoned Joffrey?

I think she’s made herself believe it. Almost since being born, she’s wanted to destroy Tyrion because she blames him for taking away the one person who would have made her life better had she lived, which is her mother. She holds Tyrion responsible for all the shitty things in life and when Joffrey dies it’s painful for her, so her grief is all directed at Tyrion and turns into burning hatred. She just wants to fucking destroy him any way possible.

Did you watch the showdown between The Mountain and the Red Viper? I couldn’t believe the head-explosion ending.

I know! When I’m there and we’re filming stuff, I couldn’t watch it and had my fingers in my ears and hands over my eyes. And I love Pedro. You make friends with people and then they fucking die on this show! You’re just like, “There goes another one!” But it was pretty fucking brutal.

After that fingers-in-the-eyes scene aired, a lot of people pointed to your Instagram because you and Pedro spoiled it in a photo shoot you did for Hunger magazine a couple of months prior.

Yes! And nobody knew. You know what? We didn’t even talk about it, we just did it. I had black nails and I was thinking, “He’s got these cute, chocolate brown eyes…” and we’d both recently come back from shooting all that, so I just thought, “I wonder if I could do the same?” [Laughs] But I will miss Pedro. He’s a great dude. And I’ll miss Jack [Gleeson]. All my drinking buds are gone!

Speaking of your Instagram, a lot of people pointed to another photo you posted and thought it gave away the arrival of another character this season. Turns out it didn’t.

My stone heart! That was in Palm Springs and I found these stones and thought, “Oh, I’ll make a heart,” and I couldn’t believe people were freaking out about it.

As far as the cast all hanging out when the cameras stop rolling, do you have a favorite off day where you all, say, went out and let loose?

We went on a boat in Croatia, which was really fun. We toured all these little islands, drank lots of wine, and it was really fun. It was all the people from the Purple Wedding—whoever we could squeeze on the boat!

What was it like to be a guest judge on Ru Paul’s Drag Race? That show is crazy—in a good way.

To get to be there and almost touch the queens as they lip-synched was one of the highlights of my life. It was great. I love the show, I love what it stands for, and Ru is a total genius.

The IMDB tells me you’re in a sequel to The Mortal Instruments?

Nope! That’s not happening. Next! [Laughs]

[Laughs] Back to Thrones. When do you start shooting Season 5?

We start end of July.

You have to verbally undress so many people as Cersei. What was the most difficult scene for you to shoot this season?

When Jack was lying on the altar with the stones, that was really hard for me because I got a bit giggly. Those are my challenges: not being an idiot. I had to ask Jack to remove the stones, and we were making each other laugh, which is what we do. And the scene with Charles where I tell him about his legacy was hard because it was so complicated, and I wanted to capture both the child that she still is with him, as well as the confidence after having three children of telling him to fuck off. And she’s also terrified of what she’s saying, too.

Lastly, have you ever gone out in public in the blond wig?

You know what, I did! Once they pushed my scene to late in the day and I already had the wig on and didn’t want to take it off so I went walking around the Belfast Shopping Centre. I don’t think anyone really recognized me, they just thought I was a bit mad. “Why does she have this weird, blond wig when she’s clearly not a blonde?”