The Hōgyoku (in Japanese: 崩玉, Crumbling Orb; Viz: "Breakdown Sphere") is a mystical item that can take down the barriers between Soul Reapers and Hollows, allowing for the creation of an Arrancar, a Hollow with Soul Reaper powers, or a Vizard, a Soul Reaper with Hollow powers. Kisuke Urahara invented this item, and Aizen stole it from Rukia, whose body Urahara had sealed the Hogyoku in. Aizen uses the Hogyoku to create an army of Arrancars in preparing to overthrow the king of the Soul Society.