Cerasormr, the Horned Serpent pokemon
Cerasormr is a very large water-and-dragon type pokemon allegedly native to the Osai region. It is a legendary creature that very few people have ever seen. Cerasormr is the name given to it by settlers - its real name is kept secret by the native Osaigon, who believe that they hide themselves from the settlers' descendants even today. Cerasormr can raise storms and call down thunder but it is not an evil creature - it is said to guard places of great power and importance, so it only unleashes its powers to protect them from interlopers. If a fog suddenly comes up from inland, rather than the sea, it is surely the work of cerasormr.