Eldest daughter of Lord Tywin Lannister of Casterly Rock, Cersei is twin to Ser Jaime Lannister, the Kingslayer. Blonde, green-eyed, and one of the most beautiful women in the Seven Kingdoms, she has the Lannister pride and the ferocity of the mother lion when her children by King Robert are endangered. Her marriage to the king is loveless—a political marriage only, to secure her father’s allegiance after Robert won the Iron Throne—and their conflicts can be brutal. Her brother Jaime is often by her side, serving as her sworn shield as one of the knights of the Kingsguard. Her other brother Tyrion, however, is an affront to her sensibilities, and she denigrates the Imp mercilessly.
Angry at her father dispatching Tyrion to act as Hand in his stead, she is reluctant to work with her brother, and the two scheme against one another instead as Tyrion tries to undo what harm she has done, and has allowed Joffrey to do. Robert’s bastard children are all found and murdered by the gold cloaks, initially in what seemed to be Cersei’s own doing, but she later admits to Tyrion that it was Joffrey who decided that the children should die so as to end rumors that he himself is illegitimate. Matters grow uglier as Stannis Baratheon’s host nears, until Cersei is convinced Tyrion means to make sure Joffrey dies. She seizes hold of his “whore”—mistakingly believing Ros to be his lover—and threatens her life if anything happens to Joffrey. Tyrion proceeds to lead a successful, bloody defense of the city, while Cersei grows increasingly drunk in Maegor’s Holdfast. When she believes that the walls have been breached, she prepares to poison her own son Tommen, only to discover joyously that it is her own father with the Tyrell host at his back. Tyrion, gravely injured by the Kingsguard knight Ser Mandon Moore, is shuffled into an out-of-the-way cellar at Cersei’s behest.