Ōin

The is an artifact that belongs to Soul Society's Royal Family, and is moved from its storing place to another every few decades.

Summary
In the movie Bleach: The DiamondDust Rebellion, this artifact serves as part of the main plot. The main antagonist, Sōjirō Kusaka, and his two Arrancar followers took the item during its transport for his plan. Kusaka attempts to get Tōshirō Hitsugaya to use his Bankai to break the seal, but instead uses his own sword. Doing so turns him into a large purple ice dragon. Afterwards, the Reiatsu created by the seal took the force of four captains to fend off. Only the combined force of Ichigo Kurosaki's Hollow mask and Hitsugaya's Bankai was able to stop Kusaka.

Powers & Abilities
Dimension Control: If a person has full control over the Ōin, then the person has absolute control over the dimension as they see fit, including the manipulation of time, energy, space, and matter.

Teleportation: Given that the seal can manipulate space, it can give the user the ability to teleport any amount of distance.

Healing: Given that the seal can manipulate time, if the user is hurt, they can transfer their body back to the way it was any time before

Requirements: For a person to fully control the King's Seal, they need to have the power of a Bankai. If they haven't achieved this, the seal's power will expand at a dangerous rate and cause mass destruction.