The sword was forged at some point during the reign of En Sabah Nur. The mage known as Myrrden Emrys (later known in history as Merlin) imbued it with his magical arts specifically to counteract Nur's healing factor. Although the sword did cause Nur severe injuries in battle, Merlin was unable to fully kill him, and only succeeded in sealing him beneath the Great Sphinx.
The sword eventually was bequeathed to a young warrior named Artorius, later to be known as King Arthur, whom Merlin chose as his personal champion to combat a fell sorcerer. Merlin kept the sword after Arthur's death.
In the present time, with his old foe freed from his prison, Merlin chose a new champion to wield Excalibur, Brian Braddock (Captain Britain). Brian took up the sword and immediately used to inflict a wound on Apocalypse, who was forced to retreat.
Background information Edit
In the Arthurian Legend, Excalibur is the personal weapon of King Arthur, sometimes attributed with magical powers or associated with the rightful sovereignty of all of Great Britain.
In some versions Excalibur and the Sword in the Stone (the proof of Arthur's lineage) are said to be the same weapon, but in the original version they are considered separate things in general.