The legendary Excalibur is initially obtained in the Merlin's Crystal quest, where it is used to free Merlin from his crystal prison. In the Holy Grail quest, it is used to kill the Black Knight Titan (level-120). This weapon has a special attack that, when activated, increases your defence level temporarily. To obtain another if you lose it, pay the Lady of the Lake 500gp.
Power Usage: 100%