Legendary Jewel

The Legendary Jewel is one of the four Legendary Weapons from Glass' World. It is currently being held by the Third Army.

Overview
The original wielder of the Legendary Jewel was summoned alongside Kizuna as well as the wielders of the Legendary Ofuda and Legendary Blunt Instrument. However, due to interference from the organization behind the waves, this wielder believed that they were playing a game - similar to Ren, Itsuki and Motoyasu when they were first summoned. As a result, the wielder of the Jewel did not take their role seriously and they believed that the waves were merely an update to the game.

However, eventually the wielders of the Jewel, Ofuda, and Blunt Instrument were killed by the Vanguards of the Waves. Miyaji and the Harpoon Reincarnator claim that they were not worthy for the roles they were summoned for. They took the three Legendary Weapons for their own experiments. As a result, they were able to suppress any spirit weapons, skills and magic from Raphtalia's World and create the Artificial Behemoth and Metal Magic Dragon. These last two had one of the captured Legendary Weapons inside of them with all of the power-up methods applied.

Power-up Method
As a Legendary Weapon, the Jewel has more than one power-up methods. They were discovered by Naofumi and his party after the Demon Dragon Emperor absorbed knowledge from the Metal Magic Dragon. As of Volume 19, three power-up methods are known. This consists of the weapons core or passive power-up method and two active power-up methods.


 * Sharing (core): Power-up methods from other legendary weapons and vassal weapons can be shared between each other. While this works without knowing the power-up method, knowing that this is the Jewel's power-up method greatly magnifies the effect of shared power-up methods. This is similar to the Legendary Shield of Raphtalia's World.
 * Trust: Trusting and being trusted leads to increased abilities. This is similar to the Legendary Shield of Raphtalia's World.
 * Profession: The user is able to select and level up professions like wizard, monk and ranger by providing various items. This is similar to the job levels power-up of the Legendary Bow.
 * Unknown Power-up Method: The third active power-up method is unknown.

Trivia

 * It is believed that jewel magic from Glass' World is meant to be a replication of the Legendary Jewel's power.