This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Cat Sidhe (Scottish)
The cat-sìth, in Irish, is a fairy creature from Celtic mythology, said to resemble a large black cat with a white spot on its chest. Legend has it that the spectral cat haunts the Scottish Highlands. The legends surrounding this creature are more common in Scottish folklore, but a few occur in Irish.
Some common folklore suggested that the cat-sìth was not a fairy, but a witch that could transform into a cat nine times. The cat-sìth is all black with the exception of a white spot on its chest. It is described as being as large as a dog and chooses to display itself with its back arched and bristles erect.