This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
British Big Cat (English)
In British folklore and urban legend, British big cats refers to the subject of reported sightings of non-native, typically large felids feral in the United Kingdom. Many of these creatures have been described as "panthers", "pumas" or "black cats". A medieval Welsh poem Pa Gwr in the Black Book of Carmarthen mentions a Cath Palug, meaning "Palug's cat" or "clawing cat", which roamed Anglesey until slain by Cei. In the Welsh Triads, it was the offspring of the monstrous sow Henwen.
There have been rare isolated incidents of recovered individual animals, often medium-sized species such as the Eurasian lynx, though in one 1980 case, a puma was captured alive in Scotland. These are generally believed to have been escaped or released exotic pets that had been held illegally, possibly released after the animals became too difficult to manage or after the introduction of the Dangerous Wild Animals Act 1976.