Excalibur

History
Excalibur was a Holy Sword produced in Avalon by Vivian as a gift to King Arthur after Arthur broke Caliburn. Vivian, seeing that Merlin had entrusted Arthur with Caliburn, saw that Arthur was worthy of an even more powerful sword, and crafted Excalibur. Arthur used it as his weapon throughout his wars until it was destroyed at the Battle of Camlann when it clashed against Clarent.

Power
Excalibur is far superior to Caliburn as a sword, and is stated to be able to destroy the entire landmass of Britain. Wielding it, Arthur became comparable to Lancelot with its full power.

Moon Wars
During the Moon Wars, the sword was brought back by destroying Clarent to be used as a catalyst for Merlin's Resurrection Ritual to bring Arthur back to life.