Object worn either to disguise or protect the face or to project the image of another personality or being. Masks have been used in art and religion since the Stone Age. In most primitive societies, their form is dictated by tradition, and they are thought to have supernatural power. Death masks, associated with the return of the spirit to the body, were used in ancient Egypt, Asia, and the Inca civilization, and were sometimes kept as portraits of the dead. Masks worn on holidays such as Halloween and Mardi Gras signal festivity and license. They have also been widely used in the theater, beginning with the Greek drama and continuing through medieval mystery plays, and the Italian commedia dell'arte, as well as in other theater traditions (e.g., Japanese No drama).