Medallion

A is a device possessed by select members of the Wandenreich military, including all Sternritter. When activated, it allows one to a Shinigami's Bankai, thereby stealing it and allowing it to be used as their own.

Overview
Medallions are thin, round devices that have the Wandenreich's insignia etched onto their surface. They are metallic and are roughly the size of an individual's palm. When presented to a single released Bankai in the vicinity, the device emits five streams of dark energy that cause the Shinigami's Bankai to disintegrate. The disintegrated Bankai is absorbed into the dark energy, forming a ring which then recedes into the medallion. The victim effectively loses their Bankai, and is left incapable of communicating with their Zanpakutō.

The process that Asguiaro Ebern uses to activate his medallion is more elaborate, requiring a long, drawn-out incantation. The process itself is different from the norm; the dark energy that pours out of the medallion forms a star shape, which then emits numerous columns of bright energy. This energy then envelops the intended target, disintegrating their Bankai on contact.

The medallion's owner can use the stolen Bankai's power at will, even if its original owner is dead.

Incantation
German= "Aufreide. Meer eh wolken, wolken eh regen, regen eh nebel. Sieht balle eh um sieht ballen. Wir gut freude, Danach Vrund Dill Becher!!!" English= "Melt. Sea to cloud, cloud to rain, rain to fog. That with shape to that which is unseen. After our jubilation, the chalice will be turned face down!!!" Kanji= 「溶けよ」 海よ雲へ 雲よ雨へ 雨よ霧へ 姿成すものよ 見えざるものへ 我等歓喜の末に 杯を地に伏せる さあ!!!

Limitations
The medallions have a number of limitations:
 * While a medallion can steal any Bankai, in order to properly control it, the one who stole it must be sufficiently powerful. Yhwach believed himself to be the only individual capable of controlling Captain-Commander Genryūsai Shigekuni Yamamoto's Bankai. For this reason, he ordered Royd Lloyd not to steal it.
 * For unknown reasons, the medallions cannot medalize Ichigo Kurosaki's Bankai. Yamamoto hypothesized that it is because Ichigo had only recently mastered his Bankai and it still had room to grow. Thus, because the limits of its power were unknown, the Wandenreich could not steal it.
 * While the medallion's owner is in possession of a Shinigami's Bankai, even if they are not using it at the time, they are unable to activate their Quincy: Vollständig.
 * While the Bankai can be wielded by the one who stole it, it cannot be fully exploited, its power being noticeably weaker than when used by its original owner. This can be rectified if the Quincy in question takes the time and effort to master the Bankai's usage.
 * Because the spiritual power of Hollows is essentially poisonous to Quincy, the medallion is incapable of stealing an Arrancar's Resurrección, despite it being fundamentally similar to a Shinigami's Bankai. Furthermore, by absorbing the Shin'eiyaku invented by Kisuke Urahara, which contains a small portion of a Hollow's power, a Shinigami can temporarily Hollowfy their Bankai, essentially turning it into a "poison." The Hollowfied Bankai is rendered harmful to the Quincy in possession of it, impairing their bodily functions and gradually falling apart. Simultaneously, the Bankai gradually returns to its original owner.

Possessors
†Bankai has been reclaimed by its original owner

Trivia

 * Yhwach has commanded that the Sternritter who medalized the Bankai of a captain is the one who will kill that captain.
 * While there's no difference in appearance for Bankai in the manga, the anime adds a purple coloration to the Bankai utilized by the Quincy.