Game of Thrones (2011 - ) is back, and with it comes the challenge of remembering all the faces and names that comprise its massive ensemble cast. With so many locations, houses, groups, armies, allegiances and rivalries flowing through the veins of Westeros, it's hard to remember just where everyone fits. Fortunately for you, we've done our best to create a little guide of all the major players, reminding you who they are, where they fit, and why they matter. Since nobody has the time to read up on absolutely everyone in the immense Thrones world, we highlighted the characters that are still alive and capable of making an appearance on the series, as well as those who are still mentioned or have had a lasting effect on those surviving.
Needless to say, this article contains spoilers about the characters listed. If you aren't caught up on the series, look no further.​

The Freys

Walder Frey (David Bradley)  

Lord of The Crossing and head of House Frey, a vassal to House Tully, Walder's family house is known for its fertility and descendants. Walder has fathered trueborn and bastard children too numerous to mention and has had eight wives, many of whom are decades his junior. He is a slippery character whom few trust. In the first season, in exchange for the Frey family's loyalty to Robb Stark's (Richard Madden) war efforts, Robb agrees to marry one of Walder's daughters or granddaughters. By Season Three, Robb had betrayed that vow and taken another wife, Talisa (Oona Chaplin), and impregnated her. Walder Frey retaliates by ordering his men to murder Robb Stark, Talisa, and Robb's mother Catelyn (Michelle Fairley) in his great hall during the wedding of Edmure Tully and Roslin Frey. The wedding becomes known as "The Red Wedding," and Walder's efforts are rewarded by Tywin Lannister by giving him Riverrun and protection from vengeful northerners. That is, until he is murdered by Arya Stark (Maisie Williams) in revenge for her brother and mother.
 

The Boltons

Roose Bolton (Michael McElhatton) 

Lord of the Dreadfort and head of House Bolton, Roose is the current ruling leader of the North after usurping the position from the Stark family to whom it serves as vassal. He is the father of Ramsay Bolton, a legitimized bastard son. The Bolton house sigil is a flayed man, respresentative of their violence and renown for flaying the skin from their enemies as a means of torturous execution. Originally fighting for Robb Stark early in the War of the Five Kings, Roose informs Robb and Catelyn when Theon Greyjoy (Alfie Allen) assaults Winterfell in their absence. One of his men is responsible for the capture and hand-removal of Jaime Lannister (Nikolaj Coster-Waldau), an act for which he spares Jaime's life in turn for not revealing he was behind the attack. During the Red Wedding, Roose reveals that he had been secretly plotting to bring down the Starks, stabs Robb Stark in the heart ,and utters the now-famous line, "The Lannisters send their regards," a message Jaime Lannister instructed he give Robb. Later, back at the Dreadfort, he finds his son Ramsay has taken Theon Greyjob hostage and tortured him, now referring to him as "Reek." Roose isn't thrilled about Ramsay mutilating a valuable hostage. After discovering that the two youngest Stark sons and Jon Snow (Kit Harington) are all alive, Roose sends lackeys to find and kill them. He eventually grows appreciative of Ramsay's grotesque but effective methods and legitimizes him as Ramsay Bolton, and the two set up shop in Winterfell as the new wardens of the North. There, his wife gives birth to a baby boy. Fearing for his legitimacy as the Bolton heir, Ramsay stabs Roose in the heart, then feeds his wife and newborn baby to the dogs.

Ramsay Bolton (Iwan Rheon)

Formerly known as Ramsay Snow, he is the legitimized bastard son of Roose Bolton. He is psychotic, dangerous, and takes pleasure in torture and mutilation. He keeps a pack of dogs which he uses for hunting and to whom he feeds many of his victims. Following Theon's Sack of Winterfell, Ramsay takes Theon to the Dreadfort and gruesomely tortures him. Much of Season Three, where Ramsay first appears as a prominent character, is dedicated to his long and extensive torture practices that indicate he is not only comfortable turning the human body inside out but is also a crafty and skilled manipulator capable of great deceit and coersion. When he finally releases Theon from his restraits, he is broken. Upon seeing the effectiveness of Ramsay's tactics, Roose Bolton legitimizes him as heir. In Season Five, his father arranges Ramsay's marriage to Sansa Stark in an attempt to placate the unhappy Northerners under Bolton control. After the couple is wed, Ramsay rapes and beats Sansa on a nightly basis until he goes out to fight the evening Stannis Baratheon (Stephen Dillane) raids Winterfell, during which Sansa and Theon escape together. Upon the birth of his father's new male child, Ramsay fears for his inheritance as the Bolton heir and murders his father and feeds his stepmother and new baby brother to the dogs, ensuring he is the only Bolton. When his position in Winterfell is challenged by Jon Snow and the wildling army, victory seems certain until Littlefinger (Aiden Gillen) shows up with the Knights of the Vale. Ramsay is confronted and pummeled to near-death by Jon. His demise comes courtesy of Sansa Stark, who allows Ramsay's ravenous mastiffs to eat him alive.

The Martells

Doran Martell (Alexander Siddig) 

The head of House Martell and ruling Price of Dorne, he is the older brother of Elia (unseen on the series) and Oberyn Martell and the father of Trystane. He suffers from severe gout and is restricted to a wheelchair. A pensive and patient man, Doran tends to favor problem resolution that avoids conflict and war. His house notoriously hates the Lannister family. Following Oberyn's death, his former paramour Ellaria Sand is perturbed by Oberyn's lack of retaliation -- a response he justifies by the fact his brother died during a trial by combat he accepted on his own terms. Oberyn's daughters and Ellaria want vengeance. When Jaime Lannister arrives in Dorne to recover his daughter Myrcella (Nell Tiger Free), the Sand Snakes stop him -- an act which gets them arrested. Oberyn learns that Ellaria sent Myrcella's necklace to King's Landing as a threat, and Doran begins to comprehend the dissention in his midst. He allows Jaime to leave and instructs Ellaria and the Sand Snakes to end their rebellion, unaware of the fact Ellaria poisoned and killed Myrcella as she left the city. In the premiere episode of Season Six, he is murdered by Ellaria, who proclaims "weak men will never rule Dorne again."

Trystane Martell (Toby Sebastian)  

The son of Prince Doran Martell, he is proposed as a marriage candidate for Myrcella Baratheon. He does not show up in any great capacity until the series' fifth season, when Jaime Lannister and Bronn (Jerome Flynn) travel to Dorne to rescue Myrcella. He is knocked out by Bronn, and Bronn is put in prison. Doran allows Trystane to decide Bronn's sentence, and Trystane allows Bronn to live. In the premiere episode of season six, he is stabbed in the head by Obara of the Sand Snakes.

Oberyn Martell (Pedro Pascal) 

Known as the Red Viper of Dorne, Oberyn is the younger brother of Doran Martell and father of eight bastard girls known as The Sand Snakes. He is well-known for his aptitude as a fighter, his grand temper, and his skills as a lover of both men and women. Tyrion Lannister (Peter Dinklage) tells Bronn that Oberyn is famous for "Fucking half of Westeros." His nickname comes from his knowledge of poisons and his deadly fighting style. His paramour and wife in all but name is Ellaria Sand, who is the mother of five of his eight Sand Snake daughters. He has a lasting hatred towards the Lannisters, as he believes Tywin Lannister (Charles Dance) ordered the murder of his sister years ago. He arrives in King's Landing for Joffrey's (Jack Gleeson) wedding and takes a seat on the Small Council. He serves as one of the judges at Tyrion's trial for Joffrey's eventual murder and decides to fight for Tyrion's honor in a trial by combat. His opponent is Gregor Clegane (Hafthór Júlíus Björnsson), the man who raped and killed his sister. Oberyn nearly wins the fight but celebrates his victory a few moments too early, allowing Clegane the opportunity to trip him and violently crush his skull.

Ellaria Sand (Indira Varma)  

The paramour of Prince Oberyn and bastard of House Uller, she carries the surname "Sand" like all bastards of Dorne. Following Oberyn's death, Ellaria becomes increasingly violent and confrontational to those around her and begins to hatch plots with her daughters, The Sand Snakes, to punish those she feels are responsible for Obery's death. This begins with her poisoning Myrcella Baratheon to punish Cersei (Lena Headey), who, having been the facilitator of Tyrion Lannister's trial which ultimately lead to Oberyn's death, is partly responsible for it. She follows that act by murdering Doran Martell, suggesting that she will attempt to take over control of Dornish rule.

The Sand Snakes 

The eight bastard daughters of Oberyn Martell, only three are prominently highlighted on the series -- Obara (Keisha Castle-Hughes), Nymeria (Jessica Henwick) and Tyene (Rosabell Laurenti Sellers). Oberyn trained them extensively in combat. After Oberyn's death, they effectively become the henchwomen of Ellaria Sand, assisting her efforts to take over Dorne and punish those responsible for their father's death.

The Others

Jaqen H'ghar (Tom Wlaschiha) 

A mysterious man, he originally appears as a criminal arrested and put in the dungeons of King's Landing, riding in a prison party towards the Night's Watch. He smuggles Arya Stark (Maisie Williams) out of King's Landing when she is captured and put to service by Tywin Lannister and reveals that his identity is merely an assumed presentation. He is one of the Faceless Men of Braavos, an order of assassins with the ability to change their appearance at will. He tells Arya to come to Braavos and study with him if she chooses. Eventually she does, and he begins to instruct her on the methods and practices of the Faceless Men at the House of Black and White. Arya ultimately abandones the Faceless Men and Jaqen allows her to leave, as she murdered the assassin he tasked with taking her out following her betrayal of the Faceless' rules.

The High Sparrow (Jonathan Pryce) 

The leader of a religious protest group known as The Sparrows, his title is a mockery against the title of High Septon, the highest cleric and leader of the Faith of the Seven, a title to which he is eventually assigned by Cersei Lannister as a means of restoring The Faith Militant, a defunct religious military order. Under that command, the High Sparrow presides over an inquest into charges of sodemy, buggery and blasphemy against Loras Tyrell (Finn Jones) and imprisons Loras' sister, the Queen, Margaery (Natalie Dormer). He also ends up imprisoning Cersei under similar charges, a move she did not anticipate, as she underestimated the High Sparrow's devotion to piousness which renders him immune to bribery or political influence. Cersei faces the "walk of shame" as a result, walking from the Sept to the Red Keep naked as onlookers pelt her with insults, feces and rotten food. The Sparrow goes on to form a pact with King Tommen (Dean-Charles Chapman) wherein the faith and the crown are interlinked as "the twin pillars of society," giving the Sparrow even more power. Tommen outlaws trial by combat, and faced with an unwinnable trial, Cersei blows up the Sept of Baelor using wildfire, killing the High Sparrow everyone else inside.

Check out our other Game of Thrones Who's Who entries:

The Starks
The Baratheons
The Lannisters
The Targaryens
The Night's Watch and the Wildlings
The Tyrells