Spoiler warning: Do not read unless you’ve seen “Game of Thrones” episode 504, titled “The Sons of the Harpy.”

In the May 3 episode of “Game of Thrones,” we were finally introduced to three of the infamous Sand Snakes — the bastard daughters of Oberyn Martell (Pedro Pascal), the Dornish prince who met a memorable end by having his skull crushed in a battle with Ser Gregor “The Mountain” Clegane last season. Although the battle was ostensibly to determine whether Tyrion (Peter Dinklage) was guilty of murdering his nephew Joffrey (Jack Gleeson) in a trial by combat, Oberyn was really seeking revenge against The Mountain and the Lannisters for the murder of his sister, Elia Martell, many years earlier during Robert Baratheon’s uprising against the “Mad King” Aerys Targaryen.

Vengeance clearly runs in the Martell family, because — as we saw in “The Sons of the Harpy” — the Sand Snakes are now just as determined to avenge their father’s death as Oberyn was to avenge his sister’s. Oberyn’s three oldest daughters, Obara (Keisha Castle-Hughes), Nymeria (Jessica Henwick) and Tyene (Rosabell Laurenti Sellers) agreed to a dark plan cooked up by Tyene’s mother Ellaria (Indira Varma), Oberyn’s favored consort, to use Myrcella Lannister (Nell Tiger Free) to start a war between their kingdoms.

The only potential hindrance to this plan? The fact that Myrcella’s father Jaime (Nikolaj Coster-Waldau) and his sellsword sidekick Bronn (Jerome Flynn) just arrived in Dorne to rescue her, thereby threatening the Sand Snakes’ leverage. Luckily for the Dornish warriors, the captain who snuck Jaime and Bronn into the country promptly went and sold them out to Obara, robbing them of the element of surprise.

To learn more about the Sand Snakes’ vendetta against the Lannisters, Variety spoke to Keisha Castle-Hughes, the Oscar-nominated star of “Whale Rider” and a self-proclaimed “major fan” of “Game of Thrones” long before she secured the role of Obara. Below, she discusses Obara’s relationship with her sisters and Ellaria, the comprehensive fight training she went through for the role, and what we’ll see when the Sand Snakes inevitably come face to face with Jaime and Bronn.

How familiar with the books and the show were you when you got the role?

I was already a major fan. I’d read the books back in high school. I mean, I’ve been a fan of the show from day one, and so it was surreal and bizarre and exciting… There’s also an element of, it’s a bit scary entering a cast and a crew that are so well established, so I was just grateful that there was a whole group of us newbies that all got to go in together.

You and the other Dornish characters also get to introduce viewers to a whole new region, one that fans have heard a lot about over the course of the show — how does that feel?

I’m super excited; [If I had] my personal pick of all the regions to come from, I would absolutely choose Dorne. Number one, the weather is the best. And last season when Pedro Pascal came in as Oberyn Martell, as a viewer it was such a treat because the way he sounded, the way he dressed, the colors that he wore was something so different to anything that we’d been exposed to thus far, and so as a viewer I was like, “Oh my God, I’m in love with this person. Who is this, and where is he from?” And so it’s nice to be a part of the vehicle that’s showing the audiences, “hey, this is the world that he’s from.”

How would you describe Obara as a character?

Obara Sand, she’s the eldest of eight bastard daughters of Oberyn Martell. He loved each and every single one of them but I think that Obara likes to think of herself as the favorite. She wields the same weapon as her father, and she’s the most like him in the sense that she has no other aspirations. Some of her sisters have aspirations to become politicians or to become septas or to become faceless women. Obara simply just wants to grow up and be Oberyn Martell. And so the interesting thing is, she’s also very unemotional in comparison to the rest of the Dornish people. She describes herself as a warrior monk. She kills people only to take in equal measure, which sounds like it doesn’t work but in Dorne it makes so much sense. So she’s taken the death of Oberyn very hard, and so it was an interesting… there was a lot of discussion with myself and the other actors and David [Benioff] and Dan [Weiss] and the directors that we work with around how we show that without her becoming emotional — because she’s not an emotional person — but also without her seeming like she’s dead inside, because that is a very fine line. She doesn’t show a lot of emotion, and so there was a lot of work around how we show everyone how hurt she was by his death.

What was her relationship with her father like — did the producers give you any insights or did you come up with your own backstory or just draw from George R.R. Martin’s books?

It was a combination of all three of those things, of taking what George had written in the books, and also David and Dan… they’re so far into it now that I think they have a very clear vision of the entire show, which was kind of a treat to come into because they had a very clear idea of who they wanted Obara to be and who she was, her relationship with her father… The most important thing is, Obara’s backstory is that when she was six years old her father came to her after never meeting her and asked her to choose — her mother was a whore in Oldtown and he asked her to choose between the spear and her mother’s tears. And Obara, without hesitation, chose her father’s spear, walked away, and her mother killed herself because she’d lost her daughter. And Obara never looked back, which I think says a lot about the woman that she grew into.

How loyal would you say she is to Ellaria, because Obara isn’t her daughter as Tyene is, but they currently all have a shared goal.

Exactly. The interesting thing is that these girls have been brought up by a man who has set absolutely no time limits on avenging her sister’s death, and they’ve been brought up with this idea, this constant notion that “we must avenge your auntie’s death. I will avenge my sister’s death no matter how long it takes. I will get Lannister blood.” So the obvious option when he doesn’t come home alive is to avenge his death, regardless of the details, regardless of the circumstances. And so, I think Obara has seen her father with a lot of women and men in his life, and so I think she has a lot of respect for Ellaria — she can obviously tell that maybe she was one of the more important ones in his life. Right now they have a common cause, and she will work with anyone who is on her team to go out there and avenge his death.

How would you describe the power dynamics between the Sand Snakes? We’ve only seen one scene with you all so far, but Obara seems like the most independent and the de facto leader among them.

Absolutely, Obara is the leader of the three. One, because she’s the eldest; two, because she’s the best fighter of the three; and she’s the coldest, so I don’t think anyone would even bother trying to argue with her, because the concern is that she’d turn around and throw a spear at them. Her relationship with Nymeria, who’s the second sister who has the whip, is a very important one. I think apart from her relationship with Oberyn while he was alive, Nymeria is the only other person in Obara’s life that she completely trusts.

And you see from the get-go that Nymeria does nothing unless Obara gives her approval. And they’re a really wonderful duo because Obara reacts off of instinct and is very reactive, and even though she’s unemotional about it, she doesn’t have a rational bone in her body. Nymeria is much more rational and might try to think of the long game, and Obara needs someone like that in her life. In fact, Jessica — who plays Nymeria — and I had set up this backstory that Nymeria was literally the only person in the world who could tell Obara no, and she probably wouldn’t take it lightly but she’s the only person that she could ever take advice from.

It seems safe to assume that Jaime and Bronn are headed for an encounter with the Sand Snakes since the Snakes now know that Jaime’s in Dorne — what can you preview about that showdown and what it was like to film?

There’s going to be a big confrontation fight scene with Jaime and Bronn with the Sand Snakes in the Water Gardens. I personally think they deserve it, they can’t just turn up in Dorne and decide they’re going to take the princess when they want her. No, no, no, no, no! [Laughs.] As soon as I got the role, they immediately had me start training in the martial art of Wushu, which lends itself to both the meditational aspect of Obara and the warrior aspect. And so a big thing was that these three sisters, they fight simultaneously always. They never fight alone, and so a big part of our training was us all getting used to each other’s body movements, how we moved. The major thing was getting used to the sound of Nymeria’s bull whip cracking. It’s one of the loudest, most abrupt sounds I’ve ever heard, and so for the first six weeks we were in a stunt tent in Belfast every day and we just trained while Jess stood in the corner and cracked the bull whip for eight hours. And every time we’d jump. No matter what, we’d jump because you’re only human. But it was important that we got to a point where that sound became soothing, and now I can honestly say that I actually do find that sound soothing. It’s so bizarre. [Laughs.]

But it was a really important part of it, and so once we all got into rehearsing the big scene, it’s huge because there’s six people and there’s a lot of weapons, and they’re all very good with their weapons. I think the thing that I’m excited to see, especially with Obara, that she is absolutely a match for Jaime Lannister, which you don’t expect. I think it’s great because their reaction to us was like, “Oh, these little s–ts, let’s get rid of them,” and then it’s like, “These little girls actually fight really well, whoa!” And then it dawns on them who they’re fighting. They realize oh no, these are Oberyn’s daughters, they’re in trouble.

How was the process of learning to handle Obara’s spear, since as you said, it was Oberyn’s weapon of choice and something that she’s obviously grown up with?

Well, I was really lucky. I’m half Māori and so I’ve worked a lot in my life with a Taiaha which is a Māori weapon which is very similar to the spear. So it wasn’t completely foreign to me to have that in my hand, which was really nice. And the other thing is, honestly, Pedro did so much of the work for us in terms of setting the sound of the characters, the way that we were. Obara is so much like Oberyn in some aspects that a lot of it just required me to just watch him. I’ve watched his fight scene a ridiculous amount of times. While we were shooting, every morning I woke up and I watched it. It’s how I started my day every day, because it was so important that the movement was similar between the two of us. So I’m so grateful to him for having set everything for us and we just followed suit.

Have you had a chance to meet Pedro yet?
No, I haven’t. I spend so much time talking about him and talking through people to him, but I haven’t talked directly yet. I’m going to make it happen because I’m sick of saying that I haven’t talked to him, but while we were shooting we’d send him, over the course of the shoot, through David and Dan or through Indira, we sent him lots of “Hi daddy, we miss you!” selfies. [Laughs.]

“Game of Thrones” airs Sundays at 9 p.m. on HBO.

What was your favorite moment of “The Sons of the Harpy?” Are you surprised Jon Snow declined Melisandre’s tempting offer? Will Daenerys forgive Ser Jorah if he brings her Tyrion as a captive (and what’s next for her after two of her remaining allies, Ser Barristan and Grey Worm, took on the murderous rebels)? Can Stannis defeat the Boltons and restore Sansa as Wardeness of the North at Winterfell? Weigh in below.