How does Harry get a sword and how does she become a Rider?

Corlath produces a smaller sword with a blue hilt, and Harry recognizes it as the sword from her visions. Corlath notes it is Gonturan, the sword of Aerin, which has been passed down through many generations. Corlath grasps the blade of Gonturan with his right hand, slicing it, and has Harry do the same with Corlath's own sword, thus making her a King's Rider.