Excalibur

Excalibur, often referred as the Sword of the Light, Sword of Time, the Holy Sword, or the God-Slaying Sword is an magical sword in the Fantasy World once granted to an adventurer that died on Earth to be used against the Demon King. However at some point, its original owner perished and the sword was sealed within an stone, which it then went as the Sword in the Stone.