Zennyo Ryūō

Zennyo Ryūō (善如龍王 or 善女龍王; lit. "goodness-like dragon-king" or "goodness woman dragon-king", respectively) is a rain-god dragon in Japanese mythology. According to Japanese Buddhist tradition, the priest Kūkai made Zennyo Ryūō appear in 824 AD during a famous rainmaking contest at the Kyoto Imperial Palace.