Second son of House Dayne of Starfall and bearer of the ancestral greatsword Dawn, forged from the heart of a fallen star and given only to a knight of the house found worthy of the title Sword of the Morning. As a young man he won great renown in the tourney lists and crushed the Kingswood Brotherhood for King Aerys II, sparing the boy squire Jaime Lannister and recommending him to the white cloak; thereafter the two stood together in the Kingsguard, where Arthur's quiet courtesy and pale blade earned him a name as the finest knight of the Seven Kingdoms.
He rode south with Prince Rhaegar Targaryen to a tower of joy in the Red Mountains of Dorne, where Lyanna Stark was kept against the storm of Robert's Rebellion. When Eddard Stark and six companions came to her at the war's end, Ser Arthur and two of his sworn brothers stood the door for the prince who would not come. Six of seven northmen died in the fight that followed, and only Lord Eddard and Howland Reed walked away from beneath the tower; Dawn was carried home to Starfall and laid in the crypts beside the Lord Commander Ser Gerold Hightower's white cloak, while the Sword of the Morning's name passed into song.