Never underestimate a Sand Snake, much less three of them.

On Game of Thrones (Sundays, 9/8c, HBO), Jaime Lannister (Nikolaj Coster-Waldau) has infiltrated Dorne in hopes of rescuing his niece/daughter Myrcella (Nell Tiger Free), but he'll encounter unexpected resistance from three warrior sisters known as the Sand Snakes. Introduced briefly earlier in the season, the Sand Snakes will be front and center of the action when the series returns to Dorne.

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The eldest of the Sand Snakes is the spear-wielding Obara Sand, played by Oscar nominee Keisha Castle-Hughes. The actress is familiar with playing fierce women who challenge the established patriarchy, having won acclaim for her breakout role as Whale Rider's Pai, a 12-year-old Maori girl who must prove she's worthy of leading her tribe. Castle-Hughes acknowledges there are parallels between Obara and Pai.

"They're very different characters, but I can see the similarities in being very strong, determined women," the actress tells TVGuide.com. "I think Pai is definitely a way softer, gentler person than Obara is. There are some obvious similarities between the [traditional Maori weapon] taiaha and the spear."

Wielding weapons are just part of what makes Obara such a threat to the one-handed Jaime. Here's a breakdown of what it takes to be a Sand Snake:

1. Be Dornish: Beyond just living in the southernmost region of Westeros, the Dornish cultural identity is tied up in being stubborn and unbeatable, hence their motto, "Unbent, Unbowed, Unbroken" (and the title of Sunday's episode).

"The Dornish have never been defeated by any other region, so they've never bowed to another king apart from their own; they've never been bent and they've never been broken as a people," Castle-Hughes explains. "A lot of it is a geographical thing, it's a very difficult place for people to invade without the Dornish being able to have enough notice to fit up an army that would defeat whatever was coming your way. This makes sense as to why Jaime makes the decision to go in incognito with Bronn (Jerome Flynn) because taking an army wouldn't work. In the books, they are also the only people that are able to tame the dragons apart from the Targaryens, which is why Elia Martell, who was Oberyn's sister whom the prince of Dorne spent his life trying to avenge, was married to [Rhaegar Targaryen.]"

2. Be a bastard child of Oberyn Martell, aka the Red Viper (Pedro Pascal): Literally, to be a bastard of a noble in Dorne means that your last name will be "Sand" by default. As a prince of Dorne, Oberyn apparently fathered his share of bastards, which comprise the Sand Snakes: Tyene (Rosabell Laurenti Sellers) with his lover Ellaria Sand (Indira Varma), Nymeria (Jessica Henwick) and Obara.

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"Although they're badass and they're warriors, they also have existed in a part of the world where they are part of the royal family and yet they don't have any responsibilities because they're bastards and don't have a right to the throne," Castle-Hughes says. "So in some ways, they've been living in an ideal situation their whole lives. And I don't imagine that Oberyn was the strictest father. I think he was a fantastic father, but I don't think there were a lot of rules in terms of how they act."

Learn more about what it means to be a Westerosi bastard and specifically a Dornish one (around the 2:10 mark) below:

3. Pick the spear: Oberyn wasn't a completely unreasonable father and let his children decide if they wanted to follow his way of life. "There's a story... where Oberyn came to claim his first daughter [Obara] from the mother," author George R.R. Martin says. "She was crying, 'Don't take my daughter away from me!' He threw a spear at girl's feet and said, 'It's a dangerous world. Choose your weapon: tears or the spear.' And she picked up the spear. And he taught her how to fight. Each of the Sand Snakes has their own distinctive weapon. Each of them defends themselves in what is a dangerous, patriarchal and in many ways a brutal, merciless society."

4. Have revenge in your blood: Being one of Oberyn's by-blows also comes with a unique outlook in life, one in which paying debts in blood makes sense. Castle-Hughes says, "Obara has been brought up as a warrior and she's been brought up with the concept and the idea that her father spent his whole life saying to his daughters, 'I will avenge the death of your auntie [Elia Martell], no matter what, no matter how long it takes. We will get the blood of the people who killed her.' The most obvious thing to Obara when her father doesn't come back alive is to avenge his death, no matter what."

5. Choose your poison: Although one of the Sand Snakes in Martin's novels actually did use poison as her weapon of choice, their TV counterparts all wield physical ones. Obara, like her father, uses the spear, while Nymeria prefers the whip. Tyene wields double daggers. Learn more about their respective weapons at the 1:17 mark below.

6. Love/live your armor: "We named her Drama Obara because she never takes her armor off, even in the most ridiculous situations because she's always ready to fight," Castle-Hughes says. "This hasn't been a lifelong thing but since the death of her father, she's had her armor on, she's ready to go. Nymeria is much more ladylike, and so there are armor-like elements to her costume, silks are there, and it's a little bit nicer. Tyene definitely inherited the more fancy gene of the three of us, and so wears the least. She's much more like her mother than papa, that's for sure.

"A really important part of the costumes was that we could move in them when we were fighting," the actress continues. "They were all specifically designed for our bodies, and then we broke them in ourselves, with our movements. The first few weeks were painful because you had leather chafing under your arms and stuff. Once it softened up, it was really easy to move and work in."

7. Learn moves like Viper: Castle-Hughes says, "Obara has spent most of her life trying to be the most like Oberyn. She wields the same weapon as him. I wasn't magically amazing at using a spear. Pedro had studied in the art of wu shu as he was training to be Oberyn, and so that was the most obvious thing [for me] as well because it was important that our movements were really similar because and that it looks like I was trained by him. You learn so much about your body and the physicality of stuff. I also watched Pedro Pascal's fight scene so many times."

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8. Stand by your sister: "They've all got different mothers, but they've all been raised at various points in their lives by the same fantastic father," Castle-Hughes says. "Obara is definitely the most independent. She's the eldest, so she feels a great responsibility to look after her sisters especially now that her father is gone. She's a very reactive person and doesn't think about things very rationally, which is where Nymeria, the second-oldest comes in, who is a much more stable person. She's looking at things and understanding the repercussions. Nymeria is the most knowledgeable in terms of what happens in the world outside of Dorne. Tyene is very young and she still has her mum, so she'll just do whatever her sisters and mum decide to do — not to say that she's not strong on her own as well, but she knows it's not her place to be making the decision."

9. Fight by your sister: "The Snakes fight simultaneously always and have each other's backs and also this spooky ability to be completely aware of each other at all times," the actress says. "So a big part of the training was literally spending as much time in each other's spaces as we could, which we did, but especially with our weapons. I don't know if you've ever heard a bullwhip crack, but it's one of the most abrupt sounds, and it's so loud and really frightening. For the first maybe six weeks of training we were in Belfast, and Jess was in the corner cracking the thing over and over again for six to eight hours a day. It took about six weeks for both Rosie and I to stop jumping every time it cracked. We had to associate that sound with a soothing sound. It was actually more comforting. We even came up with a story that when Obara was really worked up it was the only thing that would get her to sleep."

10. Meditate: That's right! Those Sand Snakes are as much into ruminating as they are into causing a ruckus. "Obara has the style of the warrior monk, and so she fights as equally as much as she meditates and reflects on what she's doing in her life," Castle-Hughes says. "In those martial arts as well, a lot of it is not just about the physicality. It really lends itself to both aspects of that, your state of mind as well as the movement. It really did help because with a character like Obara — who is very stern and aggressive and somewhat emotionally unavailable — the character could easily be played like an angry person. It was important that she wasn't that. You've got to think that there was some sort of inner peace going on, and that her reactions didn't just come out of anger, that they came out of understanding for the way that things should be done."

Are you ready to rumble with the Sand Snakes and Jaime? Watch the preview of Sunday's episode below to get a hint of what's to come:

Game of Thrones airs Sundays at 9/8c on HBO.

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