He is provided with a more appropriate sword, befitting of a king by magical means. It is a symbol of power and it is the most important item of a knight. A king would have a personal sword, an unarming sword he wore on horseback, and they had cross hilts ( to remind them of God and their fellow knights ). Arthur has two swords. Arthur has the one from the stone, to prove his kingship, and then Excalibur. It is given to him by the lady of the lake. Excalibur was for his protection, it would bring him glory and victory but the scabbard would also keep its holder from dying from his wounds.