This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Cwn Annwn (Welsh)
In Welsh mythology and folklore, Cwn Annwn, "hounds of Annwn"; were the spectral hounds of Annwn, the otherworld of Welsh myth. They were associated with a form of the Wild Hunt, presided over by either Arawn, king of Annwn in Pwyll Pendefig Dyfed, the First Branch of the Mabinogi and alluded to in Math fab Mathonwy the Fourth Branch of the Mabinogi, or by Gwyn ap Nudd as the underworld king and king of the fair(y) folk is named in later medieval lore.
According to Welsh folklore, their growling is loudest when they are at a distance, and as they draw nearer, it grows softer and softer. Their coming is generally seen as a death portent. The hounds are sometimes accompanied by a fearsome hag called Mallt-y-Nos, "Matilda of the Night". An alternative name in Welsh folklore is C?n Mamau ("Hounds of the Mothers").