Shapeshifting is a common theme in many mythologies, including Celtic mythology.
It refers to an individual’s magical ability to transform herself/himself into someone or something else, or the ability to transform others.
Aside from Arawn’s ability to transform Pwyll into an image of himself, there are several other examples of shapeshifting in The Mabinogi. These include the transformation of Gwydion and Gilfaethwy into animals, of Lleu into an eagle, and Blodeuwedd into an owl. All of these transformations occur in the ‘Fourth Branch of the Mabinogi’.