Hisako Kagine

Hisako Kagine was a Scholar, Hermit and Sorceress of exceptional power in the time before the formation of Soul Society. She was the one who first discovered how to manipulate the fragmented wills into magic, and for that reason is by many considered to be the progenitor of modern day Kidō.

Despite her power, she was a rebel by nature and refused to side with when he came to seek her aid in unifying the spirit world into Soul Society. This decision lead to a long war between the two, which eventually lead to her death at the hands of the warlord.

But with her last breath, Hisako summoned the fullest extent of her magical abilities and wove herself into the very fabric of the spiritual realms. Allowing her to return throughout the ages to instruct others in magic once more. Manifesting as the spirit of the Zanpakutō Gin'Iro Odoruchō.

Overview
While magic existed before Hisako, it was a crude and unwieldy thing to most, and few were those who ever learned to grasp its secrets. Sorcerers would jealously guard their knowledge, and even that knowledge was flawed at best, downright meaningless at worst.

As someone who believed in the wonders of the Noble Art, Hisako set out to share the gift with everyone who so desired. Teaching those who wanted to learn, both young and old, firm and infirm. Her willingness to share the mysteries of magic, and her efforts to make it more readily accessible for study drew the ire of her rival magicians, who saw her efforts as a threat to their power. Many attempts were made at her life for that very reason, but all of them failed.

Beyond her tremendous contributions to modern-day Kidō, very little is known of Hisako, as she was a private woman who never saw fit to share anything of note with her students; thus she's become an enigma, and largely lost to history as a result.

Legacy
Hisako was the progenitor of the system of spellcasting referred to by the most knowledgeable scholars as the Kagine Solution; which is based on using the fragmented wills that permeates all realms to conjure spells of exceptional power. Without this discovery, it would have been a matter of far greater difficulty to teach Shinigami the basics of Kidō.

Although few aside from those very scholars remember her name, her influence in the annals of history cannot be questioned, for without her, the world would have been a very different place indeed.