Caliburn

Caliburn also known as Collbrande, is the Cursed Holy sword of Arthur Pendragon. It is one of the five Holy Swords that was forged through the means of magic and alchemy by those who reached the territory of God, known as the Holy King Sword and the Sword in the Stone.

Summary
Caliburn is the Sword in the Stone that chooses the King in the legend of King Arthur. It is one of the two Holy Swords wielded by the Legendary King of Britain, King Arthur Pendragon of Camelot. The strongest Holy Sword, Caliburn, is the only Holy Sword to not be kept under the control of the Vatican or Heaven after the Great War, but by the Pendragon family after their move to Japan and the Japanese Hero Clan, used to seal away the evil spirit of the powerful Cadre-class Fallen Angel Kokabiel.

It has long since been kept inside a shrine located in the Japanese Hero Clan after the Great Mythology War alongside it's sister sword Excalibur, it was soon picked up by the former head Mordred who wanted to exact his revenge on the vampyres, devils and fallen angels after the war ended, but went on a rampage after he was possessed by the evil spirit that Caliburn sealed killing all the children as well as the adults protecting them.

Soon enough Arthur's power and Overdrive went out of control eliminating everything around him along with the evil spirit that was sealed in Caliburn and Excalibur leaving behind the cursed holy swords (who chose him in order to survive), himself, Tomoe, Lancelot, Elaine and an petrified and shellshocked Mordred. Arthur would soon use Caliburn and Excalibur as his swords and as a conduit to use his Banishing Shift. As shown in his fight against Ornis, whenever Arthur's life is in danger, it would also endanger its existence causing Caliburn to do whatever method required to preserve his life to where even healing wounds such as a severed arm is mended. Though Caliburn was calmed down after Rosweise offers her Ornis' soul.

Appearance
Caliburn has a grip long enough that appears as a two-handed sword with a round pommel at the end, a huge cross-like shaped guard and a long blade with a gold colored edge.

Abilities
Caliburn is the most powerful Holy Sword in existence, even after being cursed. It can generate a massive amount of Holy aura that surpasses even that of Durandal, Excalibur, and Arondight and it is powerful enough to be known as the Ultimate Holy Sword. It also has the power to manipulate space, capable of ripping through space, able to teleport the user and others into any location, and as demonstrated by Arthur, the Caliburn can open small spatial portals to teleport its blade to strike enemies from any direction unexpectedly.

Arthur is able to further synchronize with Caliburn using his unique heritage and Longinuses, letting him don a full-armored suit a lot like the one that Leohart donned.

Rosweise soon unlocked the part of Caliburn, which lets Arthur use the abilities of the souls that have been sealed within it. This is first shown as he utilizes the power of Leonard to control and enhance the Gravitational Magic, which he inherited from his mother letting him create the Banyūsekiryoku .

Trivia

 * Caliburn is another name for Excalibur in Arthurian Legend and so has the exact same meaning.