This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Puki (Icelandic)
The Puki were solitary supernatural creatures from Irish and Scottish folklore that usually appeared in animal form (a black-coated horse, goat or dog), more rarely in monstrous human form, and were either indifferent or hostile to human life and affairs. The mythological authenticity of these beings is highly debatable.
The name is clearly derived from the Irish words gabhar “goat / (white) horse or mare” and ceann” “head” and literally means something like “Goat- / Horse-headed One”. Given that gabhar is an indigenous Irish term for a goat (and a particular type of horse).