Arnold Arryn

Arnold was cousin to Jeyne Arryn, Lady of the Eyrie, and asked for her hand twice. She refused him both times. In between, Arnold and his kin twice tried to strip her of her seat, arguing that a woman had no business ruling the Vale.

After the second attempt, in 129 AC, Jeyne had him locked in the sky cells of the Eyrie. He spent years there, and when winter came he was moved to the dungeons of the Gates of the Moon. By then he was no longer himself — the confinement had broken his mind.

In 134 AC Jeyne Arryn died. On her deathbed she named a distant cousin, Ser Joffrey, as her heir — not Arnold, nor his line. Arnold, by then mad, could not press his own claim, but his son Eldric did: he won the backing of Vale lords who believed the old laws of succession should outweigh a dying woman's last wish. Lord Isembard Arryn put forward a claim of his own as well.

The Hand of the King, Thaddeus Rowan, summoned the claimants to King's Landing to make their case before the regents. It came to nothing: the regent Ser Corwyn Corbray ruled that Jeyne's will should stand, and when the others refused to accept it, he had Lord Isembard and his sons imprisoned and Ser Eldric executed.

Arnold escaped before he could share his son's fate. He fled to Runestone, the castle where he had squired as a young man, and Lord Gunthor Royce took him in. When Ser Corwyn came to the castle gates to claim him, a crossbowman shot him dead from the walls. The Vale's succession turned into open war.

From then on he was known as the Mad Heir. The houses Templeton, Tollett, Coldwater, and Dutton took his side, along with the lords of the Fingers and the Three Sisters.

Lord Thaddeus answered by sending his own son, Ser Robert, with an army across the Mountains of the Moon, and Lord Alyn Velaryon with his fleet toward Gulltown. The war for the Vale was fought on two fronts.

By 136 AC, when new regents were chosen by lot, Lord Alyn Velaryon and Lord Benjicot Blackwood had already broken the resistance of Isembard's and Arnold's supporters. All of them ended up swearing fealty to Lord Joffrey as their lord of the Vale.