Excalibur is King Arthur's sword.
In Quests of Glory, Excalibur is used as a test during Tedros' (King Arthur's son) coronation to prove he could be king. However, he failed to pull it out, which made everyone in Camelot question his leadership. Tedros soon figures how he has a half brother, who is King Arthur's eldest son, named Rhian. At the end of the story, Rhian pulls the Excalibur out of the stone, proving he should be the true king.