Elder daughter of Tywin Lannister and Joanna, born at Casterly Rock in 266 AC a heartbeat before her twin Jaime, whom she counted the other half of her own soul. Her lady mother died bringing Tyrion into the world, and Cersei never forgave the dwarf for it, calling him the Imp and worse from the cradle on. As a maid she went with a band of companions to the tent of Maggy the Frog in the woods above Lannisport, where the woods witch tasted three drops of her blood and promised her a crown of gold, a king for a husband, three children with golden crowns and golden shrouds, a younger and more beautiful queen who would cast her down and take all she held dear, and at the last the valonqar whose hands would close about her white throat and choke the life from her. Tywin spent long years pressing King Aerys II for her hand in marriage to Prince Rhaegar Targaryen, and was refused; the Mad King wed his heir to Elia of Dorne instead, and Cersei never forgot the slight. After Robert's Rebellion put a warhammer through Rhaegar's breast, Tywin gave her at last to the new king, Robert Baratheon, who took her to bed on their wedding night drunk and called her by Lyanna Stark's name, and from that hour she loathed him.
Long before the wedding her love for Jaime had become a thing of beds and bolted doors, and the three princes of the realm that the realm believed were Robert's were her brother's by blood: golden-haired Joffrey, sweet Myrcella, and gentle Tommen. When Bran Stark climbed a tower at Winterfell during the king's progress north and saw them coupling, it was Jaime who flung the boy from the window with her quiet leave. Robert's death she purchased more carefully, by setting her young cousin Lancel Lannister to ply him with strongwine on his last boar hunt in the kingswood, so that the king came home gored and emptied of blood. Lord Eddard Stark she met blow for blow in the council chamber and broke at last on the floor of the throne room, with Janos Slynt's gold cloaks at her back. Through Joffrey's reign she ruled as Queen Regent in all but name, while the realm fell apart at the seams; through the long night of the Battle of the Blackwater she sat in Maegor's Holdfast with the highborn ladies, drinking cup after cup of strongwine and waiting for Stannis Baratheon to come and kill her son. After her father came down out of the west to scatter Stannis, she gave Joffrey to Margaery Tyrell as the price of the rose's alliance, and watched her son choke to death at his own wedding feast in the Great Sept of Baelor.
Tywin's murder by Tyrion's crossbow bolt in the privy left her, at last, Queen Regent for Tommen and unchecked in her power, and she set about ruling the Seven Kingdoms as she believed her father had ruled. She drove Grand Maester Pycelle and her uncle Kevan from the small council, brought the disgraced Qyburn into her service for the dark experiments he conducted in the black cells beneath the Red Keep, and raised the brothers Osney, Osfryd, and Osmund Kettleblack high above their station, setting Ser Osmund in Tommen's Kingsguard and the others to the gold cloaks. To curb the Tyrells and clear the Crown's debt to the Faith of the Seven, she restored the swords of the Faith Militant to the High Septon she had helped raise, the gaunt holy man the smallfolk called the High Sparrow, and armed him with the very weapons that would bring her down. When she set Osney Kettleblack to bear false witness that he had bedded Queen Margaery, the Sparrow put him to the question, the confession that came back was her own, and the Faith took her into the cells beneath the Great Sept on charges of fornication, incest, regicide, and false witness. To win her trial by combat she walked her Walk of Shame shorn and barefoot and naked from the steps of the Great Sept of Baelor through the streets of King's Landing to the gate of the Red Keep, while the smallfolk pelted her with offal and called her every name she had ever feared.