Possibly the best documented skin-walker beliefs are those of the Navajo yenaldooshi, also sometimes referred to as a Navajo witch by outsiders. The yenaldooshi are evil human beings who have gained supernatural power by breaking a cultural taboo. Specifically, a person is said to gain the power of a yenaldooshi by murdering a close relative. The skin-walker will travel through the community by night, spreading misery and desecrating holy things. He or she is usually described as naked, except for a coyote skin. The yenaldooshi is also said to have the power to assume the form of a coyote or other animal.
The main power of the yenaldooshi comes from its use of corpse powder which is made from human cadavers. Touching the powder will curse a person with sickness or death. This is an inversion of the use of pollen among the Navajos, which is sprinkled to produce blessings. Another form of this is a bone pellet which the yenaldooshi will shoot into a victim's body.
In Norse folklore, a skin-walker is a person who can travel in the shape of an animal and learn secrets, or take on certain characteristics of an animal. The person is then said to be wearing that animal's hide. The most well-known example of the latter is the warrior who takes on the strength and stamina of a bear, called "bear shirt" or berserker. The use of an animal shape for other purposes was considered unmanly, and such seidmen were frequently cast out or summarily executed. Female practitioners got off more lightly, until the witch trials began in the Middle Ages and Renaissance.