Ōin

This artifact is the property of the Royal Family, and to keep it safe it is relocated from one storehouse to another once every several decades. It takes the shape of a small golden stamp worked in elaborate detail, its handle and crown ornamented with leaf-like motifs while the sides carry flowing patterns boxed into rectangles. Pressed into the underside is the inscription Tenrin Hin'in, the harmonious stamp of the heavenly wheel.

Whoever gains full mastery of the seal wins absolute authority over a dimension, bending time, energy, space, and matter to their will. That control over space grants unlimited teleportation across any distance, and the sway it holds over time lets the user undo injuries by reverting their body to any earlier moment. Unlocking this power carries a strict condition: the seal must be cut using the strength of a Bankai. Cut by someone who has never attained Bankai, its energy instead swells out of control, unleashing widespread destruction and twisting the offender into a mighty but dangerously unstable shape.

During one of its scheduled transfers, Sōjirō Kusaka and his pair of Arrancar allies ambushed the convoy and seized the seal, even though the Tenth Division captain Tōshirō Hitsugaya stood guard over it. Kusaka pressed Hitsugaya to pierce the seal with his Bankai and release its power, and when the captain refused, Kusaka slashed it himself. Lacking a true Bankai, he mutated into a huge, powerful, but wildly unstable ice dragon, and it took several captains together with Ichigo Kurosaki to bring him down. Afterward the seal was restored to the condition it held before he damaged it.