Legendary Weapons/Web Novel

The Legendary Weapons (伝説武器) are the weapons used by the Legendary Heroes. They are later referred to as the Four Holy Weapons (四聖武器) since many religions formed centering around the Legendary Heroes.

History
The worlds affected by the Waves originally had one Legendary Weapon and two Vassal Weapons. At the end of a wave cycle, two such worlds are assimilated into one, but this could be prevented by the Guardian Beasts if enough lives are sacrificed. At the arrival of Naofumi Iwatani, four such worlds have already assimilated, resulting to a total of 4 Legendary Weapons and 8 Vassal Weapons.

After the final wave the legendary weapons, except for Naofumi's Shield, gained the ability to be summoned and dispelled by their owners at any time. As a result of the world fusing with Glass' World, there became a total of 8 Holy Weapons since the world being a fusion of 8 different original worlds. While the new Heroes of the Legendary Weapons are summoned in later generations, the Shield has not reappeared due to Naofumi still possessing the Shield as a God.