It marks the beginning of the collapse of the glory of the King Arthur. When Arthur was fighting in British, Mordred rebelled. So, Arthur was forced to return to his kingdom. A fierce war took place on the mainland of Salibury. King Arthur success to kill Mordred, but King Arthur was seriously injured. On the threshold of death, he returned to Camelot.
Legend said that he threw an excalibur sword into the royal lake and he disappeared into a cave, and vowed that he would return if danger was threatened in England.