From The Golden Bough, by Sir James Frazer (the one volume abridged edition—may be lots more in the original, I don't know):
"When a Cingalese is dangerously ill, and the physicians can do nothing, , a devil-dancer is called in, who by making offerings to the devils, and wearing the masks appropriate to the them, conjures the demons of disease . . . out of the sick man's body and into his own. Having thus successfully extracted the cause of the malady, the awful dancer lies down on a bier, and shamming death is carried to an open place outside the village."
Another, longer passage, later in the book, describes how when a village in Minahassa in Celebes would suffer a series of disasters, all the people would leave the village, carrying all their household goods. After several days of sacrifices, the men, some wearing masks, some blackening their faces, all armed with swords, guns, brooms, etc. would return and rush through the streets striking walls, doors, windows, to drive away the devils. (Afterwards the priests would come in and do another ceremony, which does not seem to involve masks, so I won't describe it.)
At the new year, the Iroquois took this means of driving evil spirits from their villages. "Men clothed in the skins of wild beasts, their faces covered with hideous masks, and their hands with the shell of the tortoise, went from hut to hut making frightful noises; in every hut they took the fuel from the fire and scattered the embers and ashes about the floor with their hands."
Later in the book there is a page about a Wolf society observed among the tribes of Nootka Sound, who use wolf masks in their ceremonies, but since there is only speculation about what those ceremonies might mean I'll leave their description out. Perhaps you can look them up elsewhere and find out the occult significance, if any.
