Unnatural Advance

"Not a weapon, but a being at my disposal that will change how the inferior see the world. Finally, their eyes will be opened, with the power of the Unnatural Advance...!" - Yuuma Fujita

Unnatural Advace (不自然しんげき, "Fushizen Shingeki in Japanese lit. Advancing unnaturally"), is a powerful blue stone created by Yuuma Fujita. It's ability to control the boundary line between Hollow and Shinigami and allow either one to possess power of the other. Only one exists, and it is in the possession of Yuuma.

History
It was first debuted in Road of Curiosity, in which Yuuma used it and resulted in failure. However, towards the end it accomplished the task of evolving an adjuchas into an Arrancar. Because of the Unnatural Advance, Tobi immediately felt the spiritual pressure of it, which led him to working alondgside the creator of such a powerful weapon. In it's creation, Yuuma and his former comrade, Yū, had been secretly developing since their time in the Shinō Academy, proving their exceptional intelligence even at that time. Worth mentioning, its creation was partially attributed to Sōsuke Aizen's Hōgyoku studies. It was later used to create Yuuma's Hollow Army.

Powers
Enhanced Spiritual Power: The power of the Unnatural Advance enhanced one's spiritual power considerably. It itself has a vast amount of spirit energy embued within it, and even when grasped it can bestow Hollowfication upon another as seen when Yū was unable to handle the large amount of spiritual pressure it emitted toward him. It was stated by Yuuma that it has a Captain-Class level amount of Spiritual pressure, and those who cannot withstand that energy are induced and subsequently, hollowfied. Most notable in the creation of Yuuma's Arrancar Army they all boasted a large amount of spiritual pressure. When in use, it illuminates a brilliant coloration, and when affecting a Hollow, it consumes than in a column of spiritual pressure.
 * Hollow Dominance: Yuuma constantly displays the Unnatural Advance's ability to control Hollow. Though it is speculated he can only control weaker level Hollow, as during his escape, he was seen controlling a vast amount of Gillian to aid him. It is rumored by him, that he is capable of controlling the entire Arrancar Army with that single artifact.

Immediately Induced Hollowfication/Arrancarfication: Purposefully, the orb illuminates a bright coloration upon the being and then consumes said being in a column of bright colorations of red and then gradually changes blue. At first, the orb was rather unresponsive as Yuuma could never find a subject capble of surviving the procedure, however after some time he composed his Arrancar Army and with slightly more study he can now easily induce a Hollowfication onto any being he chooses.

Pain Inducement: The greatest flaw in the Unnatural Advance and at the same time a great motivator for all subjects who choose not to follow Yuuma. When so chosen, Yuuma can somehow influence the orb, and it then proceeds to change a darkish purple in which all Arrancar who were affected by the orb feel the same amount of pain, and can even experience death although that Arrancar doesn't have to die, it simply just experiences the pain and horror of death. Yuuma mainly uses this to strike a chilling fear into rebellious Arrancar. However, unknowing to Yuuma the very few high level Arrancar who have been bestowed with great power share the same amount of pain; a great flaw in Yuuma's Arrancar Army, as only the most powerful of subjects can feel that pain.

Subjects Exposed

 * Yū Watanabe (resulted in failure)
 * Satomi Inoue (resulted in failure)
 * Arrancar Army (evolved and took control of the Hollow)