Kyomu no Tama

Kyomu no Tama (虚無の珠, "Jewel of Vacuity"), otherwise known as the Kyomu Jewel, is a mystical and powerful artifact that had originally resided in the Valley of Screams.

History
Long before the founding of Soul Society, there was a beast of demonic proportions that threatened to destroy the balance of the soul flow. As the legend foretells, a powerful being known as Muotomo that served as an agent of the kami themselves, confronted the monster in an attempt to prevent this misfortune. The two had battled for several days in non-stop conflict, with no clear winner in sight. Desperate to protect the balance and succumbing to the realization that she lacked the strength to do so, Muotomo had allowed the beast's blade to run through her, causing his soul to merge into her body in an attempt to destroy the both of them at once. The act of doing so caused her own soul to be forced out of her body and it crystallized into what would be known now as the Kyomu no Tama. It is said that the wills of both combatants still lies within the jewel, and because of that, the Kyomu no Tama can be used for either good or evil, depending on who attempts to use it and for what purpose.

Kyomu no Tama manifested a dimension known later to the Shinigami as the "Valley of Screams" and hid itself within its confines. However, the power and aura it exuded, one filled with an absolute will, caused a strange phenomena to start occurring. The existence of Blanks was said to be an anomaly that occurs unnaturally, as souls should not be able to necessarily "fall off" the cycle of reincarnation. It was only because certain souls found themselves drawn to the jewel, believing that it could grant their desires, only to rob them of their individuality and transform them into what are known as the Blanks. The jewel would eventually accumulate the memories and personae of the souls it transformed and manifested them into a singular being known as the "Memory Rosary". Therefore, it can be said that the Kyomu no Tama causes Blanks to become created. So long as the jewel continues to exist, the existence of Blanks will continue to prosper.

Behind the Scenes
The concept was heavily inspired by the Shikon no Tama from the anime and manga series, InuYasha. However, the intention and history behind this jewel remain unique and tied absolutely into Bleach.