Excalibur

Excalibur (Caliburn in Geoffrey of Monmouth) is the magical sword owned by King Arthur, which he obtained by pulling it out of a stone to prove his right to the throne. It is said to have protected its owner from wounding in battle. When the Arthurian myths were revived in the Middle Ages, the kings of England claimed that Excalibur was still in their possession (even though Arthur is supposed to have thrown it into a lake). King Richard the Lionheart gave this alleged Excalibur as a gift to King Tancred of Sicily, after which it disappeared into the same mythological lacuna as the Holy Grail, the Ark of the Covenant, and the Lance of Longinus.