This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Mizuchi (Japanese mythology)
The Mizuchi is a type of Japanese dragon or legendary serpent-like creature, either found in an aquatic habitat or otherwise connected to water. Some commentators perceived it to have been a water deity. The term Mizuchi is the Japanese reading of several types of Oriental dragons, including the jiaolong "four-legged dragon," the qiulong "hornless dragon," or the chilong "yellow dragon."
The Chronicles of Japan Nihon Shoki makes reference to mizuchi. During the 67th year of Emperor Nintoku's reign, it is told that in Kibi province, at the diffluence of the Kawashima River, the former name of the Takahashi River in Okayama Prefecture, there dwelt a large snake or dragon that would expire or spit out its venom, poisoning and killing many passersby.