Ser Arthur Dayne was a knight of House Dayne who bore the title of "the Sword of the Morning" and a member of the Kingsguard of King Aerys II Targaryen.
Ser Arthur was the second son of Beric Dayne, Lord of Starfall. As the wielder of the sword Dawn, which had been forged from the metal of a fallen star, he bore the title of "the Sword of the Morning".
While skimming The Book of Brothers, King Joffrey Baratheon reads through the entry on Ser Arthur Dayne, mentioning his leading of the attack on the Kingswood Brotherhood and his defeat of the Smiling Knight, one of its members, in single combat. The Book of Brothers also mentions that at one point he was granted temporary command over the Kingsguard after Lord Commander Gerold Hightower suffered injuries. The entry concludes by recounting how he perished at the end of Robert's Rebellion alongside Ser Gerold and Ser Oswell Whent at the Red Mountains of Dorne, fighting Lord Eddard Stark.
Ser Arthur Dayne is seen with Ser Gerold Hightower, the Lord Commander of the Kingsguard under King Aerys II Targaryen, in a vision when Bran Stark sees into the past with the aid of the Three-eyed raven. Near the end of Robert's Rebellion, Ser Arthur and Ser Gerold were stationed to guard the Tower of Joy in Dorne by Prince Rhaegar Targaryen himself. When Lord Eddard Stark of Winterfell arrives with his bannermen, including Lord Howland Reed, in order to rescue the captive Lyanna Stark, Ser Arthur and Ser Gerold Hightower prevent the Northmen from entering the tower, peacefully. Ser Arthur is shown to be cordial to Eddard, but refuses to tell him of his sister, Lyanna Stark. Knowing there is no alternative, Ser Arthur and Ser Gerold fight the Northmen to hold the tower. Gerold is quickly killed by Lord Eddard in the melee, but Ser Arthur easily holds his own against the Northmen, cutting down most of them with two swords, and is able to disarm Eddard. Just before Dayne moves to strike Eddard down, Howland Reed - whom Dayne assumed had been mortally wounded earlier in the fight - sneaks up behind Dayne and stabs him in the back of the neck.
Ser Arthur is mortally wounded by the attack and falls to his knees, holding on to his sword for a few seconds before dropping it as his strength fades. The two look at each other as Eddard picks up the sword, seeming ashamed of how he had survived. Although in agony, Arthur's countenance is neutral, hinting acceptance of his fate and showing no sign of bitterness. With that, Eddard delivers the final blow, killing the legendary Sword of the Morning.
Considered by somethe finest swordsman in history, ser Arthur Dayne was Kingsguard to the Mad King Aerys II Targaryen. His proficiency with a sword earned Dayne the nickname,"Sword of the Morning". Howland Reed disabled the warrior in battle with a dishonorable move that saved Ned's life and allowed him to finish Dayne off.