Excalibur

Excalibur is the name of Arthur Pendragon 's mighty sword. The extent of it's power is mysterious, however one thing is clear; the only person who can wield it is the young Arthur. A magic sword that won't bestow it's power upon anyone except the one it has chosen. The mighty Zeldoris even attempts to lift the sword from it's stone and is unsuccessful in doing so. In Chapter 254, Arthur struggles to sneak into royal castle of Camelot and gain back his sword. Up till that chapter, Arthurs true strength had only been hinted at because he was separated from his sword. Arthur is clearly a very capable young king. This is shown in Chapter 234 by his ability to not only survive, but thrive and protect the ones he loves in a world seiged by the Ten Commandments reign. To be able to avoid capture or death is a feet in and of itself. However, it is undeniable that Arthur Pendragon's fighting prowess is crippled without Excalibur.

Appearance
Excalibur is a broadsword with a very wide blade. The grip has a dark swirly appearance to it, giving the appearance of a cosmic void. The cross guard has a hollow center, and a sharp diamond shape with pointed edges that matches its pommel. The rain guard is adorned with jewels, that emenate with regality.

Power Source
There is a reason why Excalibur is described as the Holy Sword. The source of its power is completely opposite of that of the Demon Clan 's. Some theories exist that perhaps the swords power comes directly from the Supreme Deity herself.