Sand Snakes

"The Sand Snakes are with me. They have the love of their people. They will avenge their father while you sit here in your chair doing nothing!"

- Ellaria Sand to Doran Martell

The Sand Snakes are the eight bastard daughters of Prince Oberyn Martell. Although noble-born bastards are often ignored by their parents, Oberyn has acknowledged and looked after all his daughters and has loving relationships with each of them. They are all loyal members of House Martell, and are treated as such by their uncle Doran Martell, the Prince of Dorne and Lord of Sunspear. Their collective nickname comes from the bastard surname used for noble bastards in Dorne and the nickname of their father: the "Red Viper." Oberyn trained the oldest three —Obara, Nymeria, and Tyene— extensively in combat.

The eldest of Oberyn's daughters with his paramour Ellaria is Tyene Sand. Ellaria is also mother to the four youngest Sand Snakes, including Elia Sand.

The Sand Snakes

 * Obara Sand, the first Sand Snake, mothered by a peasant. Named in honor of her father.
 * Nymeria "Nym" Sand, the second Sand Snake, mothered by an eastern noblewoman. Named after the Rhoynar warrior-Queen Nymeria, the original ruling Princess of Dorne.
 * Tyene Sand, the third Sand Snake, mothered by Ellaria Sand.
 * Sarella Sand, the fourth Sand Snake, mothered by a Summer Islander ship captain.
 * Elia Sand, the fifth Sand Snake, mothered by Ellaria Sand, named after Oberyn's late sister.
 * Obella Sand, the sixth Sand Snake, mothered by Ellaria Sand.
 * Dorea Sand, the seventh Sand Snake, mothered by Ellaria Sand.
 * Loreza Sand, the eighth Sand Snake, mothered by Ellaria Sand.

Personalities
The Sand Snakes are all Oberyn's daughters and raised in Dornish culture, but they have a variety of personalities that play off each other. As sisters, they might bicker on a course of action from time to time, but when faced with an external threat they will instantly band together to overcome it.

Obara, the eldest, inherited her father's martial prowess. Unlike the other Sand Snakes she is not the daughter of a noblewoman but of a commoner that caught Oberyn's eye. When she was a little girl Oberyn came to bring her to court, and made her choose between him or her mother; she chose to go with him, knowing she would never see her mother again (who later died). While the Dornish are often hot-blooded and passionately display their emotions, Obara is very taciturn, trained not to outwardly show her emotions. However, this does not mean that she is the most rational member of the group: she is in fact one of the more irrational of the sisters, ruled by her emotions. The distinction is that she will not shout or make threats if someone angers her - she will simply kill them unexpectedly, with little heed to the long term consequences. She is exceptionally skilled at combat with a traditional Dornish spear, having been trained extensively by her father.

Nymeria, the second eldest, is the daughter of an eastern noblewoman. She is the most rational and calculating of the Sand Snakes, having inherited Oberyn's cunning, evidenced by her choice of weapon: a 12 foot bull whip. In the right hands, a whip can be used for unpredictable attacks to disarm or trip up a larger opponent carrying heavier weapons, but it requires a large amount of strategy and planning during the fight in order to use effectively. In situations in which the other sisters would charge ahead, Nymeria will hold back and try to assess the situation, to calculate if it would be more opportune to wait to strike at a later time (in this she is actually somewhat like her uncle, Prince Doran Martell). Nymeria is Obara's closest confidant: she will do nothing without Obara's approval. At the same time, Nymeria is the only person (besides Oberyn) that can say "no" to Obara: to outsiders it might seem like they might be bickering, but Nymeria is the only person that Obara will even bother to heed the advice of, though she might still disagree. With anyone else, Obara doesn't even pause to listen, and simply charges ahead to do what she wanted.

Tyene is the youngest of the three (the other five are younger and not traveling with them). As the youngest, she is the most impetuous, trying to prove herself to the others, and the most overtly hot-tempered. In a situation where Nymeria would pause to assess her enemy before making a precision strike, and Obara would silently charge right in and attack with cold force, Tyene will passionately shout and threaten her enemy as she attacks them head-on. This prowess is exemplified in her choice of hand weapons: short daggers for quick attacks, which she can draw and strike with before her sisters can restrain her. She also greatly enjoys using poison against her enemies - most often using poisons to coat the blades of her daggers, as Oberyn was known to poison the blades of his spears.

In the books
In the A Song of Ice and Fire novels, the Sand Snakes are infamous throughout Dorne. Their names, in order of age, are Obara, Nymeria, Tyene, Sarella, Elia, Obella, Dorea, and Loreza. Obara was born of a prostitute from Oldtown; Nymeria of a noblewoman from Volantis; Tyene of a septa; Sarella of a trader from the Summer Isles; the rest of Ellaria Sand. Despite inheriting widely different appearances from their birthmothers, they are all said to have their father's eyes. Being Dornish bastards, they all have the surname "Sand" and are associate members of their father's House.

The oldest four are close friends and confidants of Prince Doran Martell's daughter and heiress, Princess Arianne.

Each of the eldest four Sand Snakes inherited or took after one of their father's famous traits: Obara has her father's martial prowess; Nymeria inherited Oberyn's good looks, sex drive, and cunning; Tyene has her father's skill with poisons; Sarella inherited her father's keen intellect.

The younger four Sand Snakes do not appear prominently in the first five novels, due to their ages: Elia Sand, the eldest, is fourteen years old near the end of the fifth novel, and Loreza (the youngest) is only around six years old. Elia, however, is old enough to share her half-sisters' rapport with Princess Arianne, and is just starting to be old enough to take part in the activities of her elders by the beginning of the sixth novel. Sarella has not make any appearances in the novels yet either; she is only mentioned to be at unknown location outside of Dorne.

"Tyene Sand" in the TV series is basically a combination of book-Tyene Sand and book-Elia Sand into one character. It's not clear if this means that Ellaria is also Sarella's mother in the series or if she still has a different parentage.

Doran Martell acts very cautiously when any of his nieces are present. He is aware how dangerous they are, and that their kinship will not stop them from harming him (after he caressed Tyene's head, Maester Caleotte examined his palm very carefully and thoroughly for any scratches or a particular smell to see if she poisoned him). Areo Hotah watches them closely in such occasions, ready to take action whenever they make a potentially harmful move.

On the second novel, Tyrion said "The Martells have every cause to hate us. Nonetheless, I expect them to agree. Prince Doran's grievance against House Lannister goes back only a generation, but the Dornishmen have warred against Storm's End and Highgarden for a thousand years". Tyrion was wrong at least in respect of the Sand Snakes, whose hatred is mainly aimed at the Lannisters, and barely speak about the Tyrells. The reason is perhaps that specific and recent atrocities - let alone exceptionally savage ones, as the murder of Elia and her children - are burnt in memory much more vividly than general hostilities. Morever, Oberyn's death has greatly increased the hatred the Sand Snakes feel toward the Lannisters, thus belittling any grudge (if at all) that they have against the Tyrells.

In the beginning of A Feast of Crows, the three eldest Sand Snakes come up with various plans to avenge their father, none involves harming Myrcella: Prince Doran rejects the above plans, and takes steps to prevent all his nieces from stirring up troubles, by arresting the three elder daughters and confining the four youngest and their mother to the Water Gardens; Sarella he leaves alone, as she is not in Dorne at the time. However, his daughter Arianne attempts to accomplish Tyene's plan, which nearly results in Myrcella's death: one of Arianne's escorts, Ser Gerold "Darkstar" Dayne, injures her severely and escapes. Myrcella survives but is terribly disfigured. Arianne is imprisoned, like her seven cousins.
 * Obara, who relies most on martial prowess and brute force, demands her uncle to give her and Nymeria an army, that she can sack Oldtown while Nymeria heads to King's Landing.
 * Nymeria, the most cunning of the sisters, suggests that she and Tyene will lead a precision strike: to assassinate Tywin, Cersei, Jaime, and Tommen.
 * Tyene's plan is to crown Myrcella in order to provoke the Lannisters and Tyrells into attacking Dorne, then the Dornish will bleed them in the passes and bury them beneath the blowing sands.

As much as the Sand Snakes hate the Lannisters and wish to exact revenge, they (and Ellaria Sand) never had any personal grudge against Myrcella, and never intended to harm her. They are not responsible at all to the near-fatal attempt on her life, although it can serve their purpose well,  as Obara commented.

In the fifth novel, after Ser Balon Swann arrives in Dorne to retrieve Myrcella (and to play his part in Cersei's scheme to assassinate Trystane), Doran orders the release of his daughter and nieces, and gives them tasks: Obara will lead Ser Balon in the chase after Darkstar, while Nymeria and Tyene accompany Myrcella to King's Landing; Nymeria will take her father's seat on the Small Council, while Tyene, disguised as septa, will befriend the new High Septon. All three of the Sand Snakes swear that they will serve their uncle when he reveals that he has been conspiring for years to gain total revenge on the Lannisters by working to restore House Targaryen.

As for the youngest Sand Snakes: according to Arianne's sample chapters of the sixth novel, Elia accompanies Arianne on a mission to meet potential allies; Loreza and her mother travel to her grandfather's seat at Hellholt; Obella is dispatched to Sunspear to serve as a cupbearer to the wife of the castellan Manfrey Martell; Dorea remained at the Water Gardens.

In sharp contrast to the show, as much as the Sand Snakes are angry at their uncle for lack of action against the Lannisters, none of them has ever harmed him or Trystane; even if they had such intentions, Areo Hotah would have never acted so carelessly as he did in the show: he always watches the Sand Snakes very carefully when they are around his prince (perhaps even more closely than he watches other people), knowing how deadly they are, ready to react to any potentially harmful move on their behalf. It's quite the contrary, after Doran tells them from a plot of Cersei to kill Trystane in an ambush, with the plan to get her daughter back and to blame Tyrion for this, all the Sand Snakes are shocked; Obara is outraged and wants retaliation against Ser Balon and his party who are part of this scheme.

Though in the novels the Sand Snakes are fierce warriors, they adhere to a strong code of honor and absolutely refuse to harm innocent people, unlike in the television series where Obara is presented as almost machine-like in nature, ready to commit cold-blooded murder solely for her own amusement.