Tenkuko

Tenkuko (天空子; lit. Heavenly Void Child) is a rampant zanpakutō sought after by Central 46 due to its enormous threat to the mission of Soul Society. Her owner is in comatose for an unknown amount of time – the event that placed him in a coma also resulted in Tenkuko's rampancy. However, Tenkuko was able to keep himself in control, theorized to be because of her powers as a zanpakutō.

Personality and traits
She is a selfish and arrogant spirit, though her powers contributed to the latter. Tenkuko does not appear to care about others: seeking amusement to starve off boredom. She has said that excitement is hard to come by, and that it should be relished whenever possible. She does not care whether her wielder remains in a coma or not, and has not made any effort in returning.

Powers and abilities
Tenkuko has the innate power to negate and nullify the movement of energy around him, allowing him to pass through a flurry of hadō or even stand up to most bankai with little to no effort. She can also nullify illusions before they could affect her senses, rendering such abilities useless before they could be of any use.