This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Skin-walker (American Indian)
Western Indian tribes also believed in supernatural beings known as Skinwalkers. The Navajo tribe especially believed that these Skinwalkers were shape-shifters who could assume the form of any animal which allowed them to travel quickly and gave them the ability to hide in plain sight.
They are generally said to have been evil witches capable of transforming itself into a wolf, coyote, bear, bird, or any other animal. When the transformation is complete, the human witch inherits the speed, strength, or cunning of the animal whose shape it has taken.