The Stern Ritter (German for "Star Knights") are a specific group of powerful Quincy in the Vandenreich's army, who play a pivotal role in the invasion of Soul Society, being tasked with purging the Shinigami.
While the organizational structure of the Stern Ritter is not yet clear, like certain others within the Vandenreich, each member is apparently assigned a letter of the alphabet by their monarch in order to designate them. According to Akon, the members of the Stern Ritter have equal, if not superior power compared to Shinigami Captains.
All members of the Stern Ritter wear a distinctive white, ankle-length cloak that features the Vandenreich insignia emblazoned on its back and often, a hood attached to the cloak's collar. Beneath this, the remainder of a personnel's attire usually consists of a heavily customized variant of the standard Vandenreich uniform — a white double-breasted trench coat tied with a black belt, worn with white trousers and boots.
Medallion: Like various others within the Vandenreich, all members of the Stern Ritter carry on their person a round, unnamed device that is roughly the size of a person's palm and has the Vandenreich insignia etched into its surface. When activated, this device is capable of stealing a single currently released Bankai in the immediate vicinity. The medallion's owner can then proceed to use the stolen Bankai's power at will, even after the original owner of the Bankai has died. However, they are unable to exploit this power fully, as noted by Yamamoto.