Second of his name, born to Prince Jaehaerys and his sister Princess Shaera in 244 AC and wed in his boyhood to his own sister Rhaella in obedience to a woods-witch's prophecy that the prince that was promised would come of their joint line. He passed his youth as a page at the court of his grandfather King Aegon V Targaryen alongside Tywin Lannister of Casterly Rock and Steffon Baratheon of Storm's End, the three of them inseparable, and won his knighthood on the Stepstones during the War of the Ninepenny Kings choosing to be dubbed by his friend Tywin's hand. He was crowned in 262 AC when his father Jaehaerys II perished of long illness, and he came to the throne with bright ambition — to be the greatest king the realm had known, to raise a new Wall a hundred miles north of the old one, to build a city of white marble across the Blackwater, to bring the Titan of Braavos to its knees. None of these came to pass, but for the first ten years of his reign the realm prospered greatly upon the management of his Hand Tywin, who paid off the crown's debt to the Iron Bank from the gold of the Rock and quieted every dispute in the king's name.
The marriage to Rhaella ran cold from its first night — Aerys took mistress after mistress and dismissed the queen's ladies as he had them, and Rhaella lost child after child in turn: stillbirths in 263 and 264, the stillborn Shaena in 267, Prince Daeron who lived half a year, another stillbirth in 270, miscarriages in between. By 270 he had convinced himself that none of them were his and confined the queen to Maegor's Holdfast with two septas in her bed to ensure her faithfulness. After Joanna Lannister died bringing Tyrion into the world in 273 AC he is said to have remarked the gods had taken Joanna away to teach his old friend Tywin some humility, and that was the last of the affection between them. He grew jealous of his Hand's reputation as the true ruler of the realm and tore the tongue from the head of Tywin's own captain of guards Ser Ilyn Payne for repeating it. In 277 AC, against Tywin's counsel, he rode to Duskendale to settle a small grievance with Lord Denys Darklyn and was taken captive in the Dun Fort for six months; Ser Barristan Selmy slipped in alone and brought him out, but the king who emerged from those cells was not the king who had gone in. He came back convinced his Hand had meant for him to die there so that Cersei Lannister might wed Rhaegar, and from that day he was attended only in the white cloaks' company. He grew long, ragged, and sour, his fingernails curling, his beard wild, his court ruled by pyromancers and by fear; he took to burning men who displeased him, finding the burnings a sweetness that drove him to his wife's bed.
When in 281 AC he raised Ser Jaime Lannister to the Kingsguard to strip Tywin of his prized heir and so drove the Hand from court, his ruin was begun. The next year Lord Rickard Stark and his heir Brandon rode south demanding Lyanna restored from Prince Rhaegar; the king burned Lord Rickard alive in his armour in the throne room and made Brandon strangle himself reaching for the sword to save him, and then demanded the heads of Robert Baratheon and Eddard Stark from their fosterer Lord Jon Arryn, who raised his banners in answer. The pyromancers had by then seeded caches of wildfire beneath every district of King's Landing on the king's order, to be lit if the city should fall; his last Hand Lord Qarlton Chelsted threw down the chain on learning of it and was burned alive for the throwing. When Lord Tywin's host was let through the gates at Grand Maester Pycelle's urging and began the Sack, the king sent for the pyromancer Rossart and commanded him bring his Hand's son Jaime his father's head as proof of loyalty. Ser Jaime ran Rossart down in the street and came up to the throne room with the blood still on his sword, and when the king cried again for Tywin's head he hauled the king down off the steps of the Iron Throne and opened his throat with a single cut to forestall the burning of the city. He died crying Burn them all.