Cersei Lannister

"When you play the game of thrones, you win or you die. There is no middle ground."

- Cersei to Ned Stark.

Cersei Lannister is the Queen of Westeros and a main character of a Song of Ice and Fire. She is the daughter of Lord Tywin Lannister and twin sister (and lover) of Jaime Lannister. Cersei is one of the two main antagonists of season 1 and a secondary antagonist in later seasons. In the TV series, she is portrayed by Lena Headey.

History
Cersei was the eldest child of Tywin Lannister, Lord of Casterly Rock and Hand of the King, and of Joanna Lannister. She had a twin brother, Jaime. Since a very young age she and Jaime were engaged in an incestuous relationship until they were discovered by their mother who died before she could completely stop their relations. Lady Joanna died while giving birth to Tyrion, who was a dwarf. Her father intended to marry her to Prince Rhaegar Targaryen yet King Aerys opposed the marriage. Before this happened however Jaime joined the kingsguard so to secure a place near her sister, Lord Tywin never forgave Aerys for this and resigned his position as Hand of the King.

Sometime after it a rebellion against Aerys took place, led by Robert Baratheon. The Lannisters maintained neutrality until the very ending of the war when Tywin sacked Kings Landing and Jaime murdered Aerys. Robert Baratheon was crowned as king and, to secure her father’s loyalty, married Cersei. Their marriage was a loveless one as Robert only loved his deceased fiancée Lianna Stark and Cercei maintained (secretly) her relations with her brother Jaime and gave birth to three children thought to be Roberts yet were Jaime’s.

When Roberts’s hand, Jon Arryin, died under mysterious circumstances Robert decided to recruit his childhood friend Ned Stark as Hand of the King. When they were visiting Winterfell Ned’s son, Bran, saw Jaime and Cersei having sex. In an attempt to conceal the truth by trying to kill him, Jaime threw Bran of the window. While they returned to Kings Landing an assassin tried to murder an unconscious Bran rising suspicion on the Lannisters. Lady Catelyn, Ned’s wife, kidnapped Tyrion which caused a war between Lannisters and Starks. Ned, investigating Arryin’s murder found the truth about Cersei’s children and led by honor warned her about the risk under which she would fall once Robert Found out. Before Ned could tell Robert, however, Cersei murdered her husband by causing him to get excessively drunk during boar hunting. Her eldest child Joffrey was named king while she imprisoned Ned Stark for treason. Meanwhile her brother Jaime was captured by the men of the Starks. The Lannisters intended to use Ned to buy peace with the Starks yet Joffrey had he executed. In his place Tywin was appointed as hand of the king.

Stannis Baratheon, Roberts’s brother, had found out the truth about Cersei's children and claimed the crown for himself, just as his younger brother Renly, Robb Stark, Ned’s heir, sought to become an independent monarch as Balon Greyjoy. Civil War broke and Tywin sent Tyrion as his Hand Representative. Tyrion and Cersei had clashing views yet Tyrion managed to outsmart her and took most of her power away. Everything went wrong for him however when Stannis laid siege to Kings Landing and Lord Tywin returned to defeat him and claim his place as Hand of the King. Renly, Robb Stark and Balon Greyjoy where murdered and the only one to oppose the Lannisters rule was Stannis Baratheon.

The Lannisters intended to forge an alliance with the Tyrells, one of the most powerful families on Westeros, by marring Margaery Tyrell to Joffrey. This however failed when Margaery’s grandmother, concerned with Joffrey’s cruelty, poisoned Joffrey during their wedding. The blame however fell on Sansa Stark, who was being held as a hostage, and on Tyrion Lannister. Tyrion was imprisoned yet Sansa disappeared. Her brother Jaime was released from his imprisonment and arrived to Kings Landing to help her mourn their dead son (even though Jaime had no love for Joffrey). Tyrion was going to be executed yet he escaped with the help of his brother and killed Lord Tywin, leaving Cersei with all the power.

Margaery married the new king Tommen who was just a child and had a sweeter nature than his brother and mother. Instead of unifying the realm Cersei tried to undermine the Tyrells by claims against Margaery’s virginity and giving religion more power, yet this plan backfired when all of her lovers where discovered. The faith imprisoned her. During her imprisonment her uncle Kevan ruled as regent and he improved the relations with the Tyrells by naming Lord Mace Tyrell as Hand of the King. However his rule was short lived because he was murdered by Varys. She is going to be judged by a trial by combat with her champion being Ser Robert Strong.