The dancer who wears a mask in a ceremony is frequently believed to be transformed into or possessed by the spirit inhabiting or represented by the mask. Masks are often believed to contain great power, being potentially dangerous unless handled with the proper rites. The manufacture of a mask may also be subject to prescribed observances. Iroquois false-face masks, for instance, must be carved from a living tree, which must be ritually asked to grant permission for the carving and must be offered Ritual masks generally depict deities, mythological beings, good and evil spirits, spirits of ancestors and the dead, animal spirits, and other beings believed to have power over humanity. Masks of human ancestors or totem ancestors (beings or animals to which a clan or family traces its ancestry) are often objects of family pride; when they are regarded as the dwelling of the spirit they represent, they may be honored with ceremonies and gifts. The fearsome 6-m (20-ft) high totem masks of the Papuans of New Guinea are believed to frighten away evil spirits and thus protect the living. Totem, ancestral, and other spirit masks are frequently used in initiation ceremonies, and the initiation masks of West Africa are renowned for their beauty. In agricultural rites, masks may represent rain or fertility deities; similarly, animal masks may be worn in ceremonies to ensure a successful hunt. Shamans throughout the world wear masks in curative rites. In East Asia and Sri Lanka, masks may be worn to protect the wearer against (or to cure) diseases such as measles and cholera. In some cultures, masked members of secret societies (such as the duk-duk of New Guinea) terrorize wrongdoers and thus enforce social codes. In parts of Africa, legal judgments are pronounced by masked judges; a historical European analogue is the masked executioner. In festivals in Mexico and other countries, masks may be used for entertainment, storytelling, caricature, and social satire. Grotesque war masks were worn in battle in ancient Greece and Rome, in medieval Japan, and by the Northwest Coast peoples of North America; today, war masks survive chiefly in ceremonies.
In funerary ceremonies, masked dancers may seek to drive the soul of the deceased into the spirit world, where it will not harm the living. In memorial rites, masks may be worn to represent departed personages or ancestors. Occasionally, as in pre-Columbian Mexico, masks may be placed on memorial statues. Burial masks are sometimes placed on the face of a corpse (for example, by the Hopi people and in ancient Egypt, Rome, China, and Mexico), either to protect the deceased from evil spirits or, as in Egypt, to guide the dead person's spirit to its home in the afterlife. Death masks, made from wax impressions of the features of the deceased, were used in Egypt and Rome as models for sculpted portraits. In medieval Europe, the death mask itself served as a memorial effigy; this use, for famous persons, persisted into the 20th century.
Ritual masks survive in modern Western culture in various folk pageants and customs (such as the frightening Perchten masqueraders in the Tirol, and in Halloween and carnival masquerading) and occasionally in other instances.