Queen Cersei I Lannister was the twentieth ruler of the Seven Kingdoms and the widow of King Robert Baratheon, with whom she had her sole trueborn child, and the Queen of the Seven Kingdoms. She was the daughter of Lord Tywin Lannister, twin sister of Jaime Lannister and elder sister of Tyrion Lannister. She was involved in an incestuous relationship with Jaime, who was secretly the father of her three deceased bastard children, Joffrey, Myrcella and Tommen, as well as an unborn child.

After the poisoning of her elder children in the later stages of the War of the Five Kings and Tommen's suicide in the wake of the destruction of the Great Sept of Baelor, Cersei assumed the throne under the name of Cersei of the House Lannister, the First of Her Name, Queen of the Andals and the First Men, Protector of the Seven Kingdoms, making her the twentieth ruler of the Seven Kingdoms (as well as the first officially recognized Queen Regnant in the history of Westeros).

Actor must be able to do a London-based English accent. Cersei is cold, calculating, and extremely selfish. She does not suffer fools and enjoys turning the tables on her enemies. She has a long memory for people that wronged her, and holds grudges until they are dead.