Manning Nash found that witchcraft was alive and well in this country even in the 1950s. He said that in the nine months that he spent in Amatenango, every two months a man was murdered for being a witch.
The people in this region believe some men have animal twins called nawales.The nawal is the source of power in medical practice and all curers must have at least one nawal in their possession. A man's nawal is revealed to him in a dream later in life, however, he has possession of one from birth. These men use their power, which is essentially a medical and curing power, to keep the pueblos free from sickness.
However, as I mentioned at the beginning of this piece, at least one man was murdered every two months or so for misusing his power to heal. A nawal that turned vicious injected illness and ate the souls of the victims. A man's nawal assisted him in healing others, but when the nawal turned vicious, the man had to be put to death.
clipped from www.monstropedia.org
Within anthropology, Nagual is most commonly used negatively to refer to a person who has a particularly strong animal companion and who uses this companion to cause harm to others, or who himself changes shape into animals in order to cause harm to others. The normal practice is to refer to the animal companion itself as a Tonal, following the Aztec practice.