Palace of the Dragon King

Taking the shape of a black box, it can be used to expose a gaseous substance to a person, petrifying their entire body, resulting in them being preserved alive for ten thousand years.

## Etymology [ ]

The technique is named after " Ryūgū-jō ", an undersea palace of Ryūjin . It also appears in the tale of Urashima Tarō , the same tale Urashiki is based on. Also, the box shape and its time freeze property could be an allusion to Tamatebako , the box Urashima received in Ryūgū-jō, which later turned him into an old man after the centuries he spent in Ryūgū-jō without ageing.