Born in 88 AC to Ser Otto Hightower, younger brother to the Lord of the Hightower, and brought to court at thirteen when her father was named Hand of the King in 101 AC. Precocious then and clever and lovely at eighteen, she became the constant companion of the failing Jaehaerys I, fetching his meals, helping him wash and dress, and reading to him; at the end the old king sometimes mistook her for his daughter Saera, and it was Alicent who was reading to him when he died in 103 AC. She stayed on at court under Viserys I, and when Queen Aemma Arryn died and the small council pressed the king to wed again, Viserys ignored every name they put to him and chose her. They married in 106 AC over whispers that the Hand had risen above himself, and darker ones that she had come to the king's bed while Aemma still lived.
She bore Viserys four children in quick succession, Aegon, Helaena, Aemond, and Daeron, and her warmth toward her stepdaughter cooled as Rhaenyra remained heir over all of them. Both women meant to be first lady of the realm and only one could be. At the tourney of 111 AC, held on the fifth anniversary of the marriage, Alicent came to the opening feast in green while Rhaenyra wore Targaryen red and black; note was taken, and thereafter men spoke of greens and blacks. She urged Viserys to wed Rhaenyra to six-year-old Aegon and was refused, on the grounds that she wanted only her own blood on the throne. Ser Criston Cole broke with the princess and became her sworn shield. After Aemond lost an eye to Lucerys at Driftmark in 120 AC she demanded the boy's eye in return, and when the king refused her she was left to keep her household at King's Landing while Rhaenyra kept hers on Dragonstone.
When Viserys died in 129 AC a servant woke her first, as she had instructed. She called Criston Cole and the small council, and they crowned her son; at the Dragonpit she lifted her own crown onto Helaena's head and named her queen. What followed took nearly everything from her. Blood and Cheese bound and gagged her in her own chambers and killed her grandson Jaehaerys in front of his mother. She yielded the Red Keep when King's Landing fell, was bound in golden fetters, and was spared only "for the sake of our father, who loved you once", while Otto and the rest of the green council lost their heads. On her knees before the Iron Throne she offered to divide the realm between Rhaenyra and Aegon and was refused and threatened with the loss of her tongue. Aemond fell above the Gods Eye, Daeron at Tumbleton, Maelor to a mob at Bitterbridge, and Helaena from a window of Maegor's Holdfast; at that last news Alicent rent her garments and cursed her rival. After her son was poisoned in 131 AC she was confined to her apartments, forbidden the court and barely trusted near her own granddaughter. In her last year she wept more than she read or sewed, tore her clothing to pieces, talked to herself, and came to abhor the colour green. The Winter Fever took her a few days into 133 AC; it gave her back her wits at the end, and she spoke of wanting to see her children again, and of Jaehaerys, but never of her husband.