King Kai or North Kai is a deity, the ruler of the North Galaxy, and Goku's final martial arts teacher, and later mentor. He also taught Yamcha, Tien Shinhan, Piccolo and Chiaotzu. His planet is at the end of a long winding road known as Snake Way, where he teaches powerful, new techniques such as the Spirit Bomb and Kaio-ken. Despite the fact that his planet is around 100 feet in diameter, its gravity is ten times greater than Earth's.