evil. Their actions are believed to be motivated by envy or hatred, and, it is feared, they may be employed by one's enemies. Sorcery often consists of poisoning, which may be counteracted by a priest or detected by a diviner, but one of the hazards of dealing with the spiritual realm is that sorcerers are sometimes disguised as priests or diviners. A person may use amulets or other objects to ward off the evil effects of sorcery, but these are sometimes powerless. Collective religious ceremonies are important to the life of many Akan peoples. The most important of these is the yam festival, which serves several functions. It is a memorial service for the dead and begs for their protection in the future; it is a time of thanksgiving for good harvests; and it is a ritual of purification that helps rid the group of evil influences. It also provides an opportunity to recall the discovery of the yam—now an important part of the diet of many Akan people—and to salute the Akan chief who, it is said, risked his life by tasting this unknown food before others in his chiefdom. The yam festival is considered vital to the group's survival, and it serves important social functions—it defines the group, symbolizes its unity, and reminds people of their obligations to others. Religion among the Kru peoples of the southwest resembles that of the Akan, with an important difference in the presence of a second powerful deity alongside the creator. This second god is an evil deity or devil, who works against the creator god, producing a duality that is an important theme in Kru culture. All individuals exhibit a balance of good and evil, in this view, and maintaining this balance is important both to the individual and to the entire universe. Religions of the north Northern religions contain the notion of dual deities found in the southwest, although the two often complement rather than oppose each other. Ancestral spirits are especially important, because it is believed that they can directly influence an individual's fortunes in this life. The cosmology of the Mandé peoples of the northwest is described in their myth of origin, variants of which are retold throughout the region. The myth recounts God's creation of the universe and of four sets of twins from seeds. They were commanded to populate the earth and teach their offspring how