Sōkyoku

The is a large halberd, which the Gotei 13 uses at Sōkyoku Hill to execute Shinigami that have severely broken the law.

Overview
When not in use, the Sōkyoku is sealed by a number of thick ropes wrapped around its pole, which pierce the ground, holding the halberd in place. During an execution, the Kidō Corps unseals it, causing these ropes to unwind and shoot off away from the Hill.

As the Sōkyoku activates, it emits an immense amount of flames, and rises into the air, pointing towards the victim, who is held before it by support beams. The flames then envelop the halberd, revealing its true form; a massive, phoenix-like entity called. In this state, the Sōkyoku’s offensive and defensive power is said to be equivalent to that of a million Zanpakutō. As it pierces the victim, this power increases by tenfold, and creates so much heat that it vaporizes their soul.

Plot
In the letter he wrote to Momo Hinamori, Sōsuke Aizen claims that Tōshirō Hitsugaya planned to use the Sōkyoku’s immense power to destroy Soul Society. However, Aizen later reveals that he needed the heat that it produced to vaporize Rukia’s soul, so that he could retrieve the Hōgyoku.

When it is used for Rukia’s execution, Ichigo Kurosaki arrives and blocks it with his Zanpakutō, Zangetsu, an act that Suì-Fēng says should be absolutely impossible. The Sōkyoku prepares to attack again, but is destroyed by Jūshirō Ukitake and Shunsui Kyōraku using the Shihōin Shield.

Appearances in other media
In Bleach: Shattered Blade, it is revealed that destruction of the Sōkyoku broke the seal that was imprisoning a powerful Arrancar named Arturo Plateado. At the same time, the Sōkyoku shattered into several pieces, even one of which could augment the spiritual power of its holder. Arturo plots to collect all of these shards, and to use their power to decimate Soul Society.