kachina mask

…a traditional ritual while wearing kachina masks and other regalia. The spirit-being depicted on the mask is thought to be actually present with or within the performer, temporarily transforming him.

Spirits called katsinas (kachinas), who—tradition holds—first brought rain to the Pueblo tribes, are said to have left their masks behind when sent to dwell in the bottom of a desert lake. The masked dancers embody the return of the kachinas to help bring the rain.