Conch shell
法螺貝 horagai

A conch blown by mountain ascetics (yamabushi) and on battlefields; as a treasure motif its voice drives away evil.
Buddhist ritual instrument; used by Shugendō mountain ascetics and as a samurai battle signal
Buddhist monks in Japan have long used the conch trumpet in rituals, and it is still blown in the Shuni-e rites at Tōdai-ji in Nara. It is closely tied to the yamabushi ascetics of Shugendō, who used it to signal across mountains and to accompany chanting. Samurai armies used a war conch (jinkai) to order attacks and retreats, often enlisting yamabushi to blow it. As a treasure motif it carries this sacred and protective role.
Yamabushi still blow the conch at mountain rites such as those of the Dewa Sanzan.