Ayakashi

The Ayakashi (アヤカシ, Ayakashi?) are ancient spirits with nightmarish forms that serve the Gedoushu, dwelling within the depths of the Sanzu River until being summoned to go through the gap. However, they can only remain in the mortal world until they begin to dry up, returning to the Sanzu River to regain their moisture. Each Ayakashi has two lives, the second life allowing them to grow giant once they are slain in human-size battle.[7] The term ayakashi refers to a damned soul lost at sea in Japanese myth. It is also homophonous with ayakashi (怪士?), a mask used to represent a ghost in Noh theater.