Leizhenzi is a celestial being that had been created by a certain great thunderstorm at Mount Swallow. Ji Chang had been the one to first receive the small newborn, and thus the baby would become known as the third son of Ji Chang. However, Yunzhongzi would take the newborn in as his own disciple, for he was destined to assist in the creation of the new Zhou Dynasty.
Seven years later, at a time in which Ji Chang was seen fleeing for his life from the capital after finally being freed, Leizhenzi, now seven, would be sitting with his master, Yunzhongzi atop Mount South End. Once Leizhenzi was told to assist his father, but first grab a hold of his weapon - which was by the cliff's edge - Leizhenzi would look everywhere in wonder. Soon enough, Leizhenzi would find two large apricots at the edge of the cliff, and eat them both with due haste. Immediately following this point, two large wings would suddenly sprout from Leizhenzi's back, and his face became like that of a monster's.
Once Leizhenzi returned to his father, he would receive a golden rod as his weapon and would be instructed to finally assist his father. Thus, once Leizhenzi met his father atop a mountain slope, he would first deal with General Lei and Yin by creating a rockslide with his golden rod. While hanging on to Leizhenzi's back, Leizhenzi would then transport his father through the five mountain passes. With these words, Leizhenzi would depart from his father: "My father, you are now safe. Now I must say good-bye and return to Mount South End. Please take care of yourself. I will see you again someday."