Chief warrior of K'un L'un, Lei Kung spent eons training young men to defeat the dragon Shou Loa and obtain the Iron Fist. And for eons, young men failed -- even Lei Kung's own son Davos, who became the embittered super-villain Steel Serpent. Then new blood came to K'un L'un in the form of mix-raced Danny Rand-Kai. From the first day of his training, Lei Kung realized Danny could indeed be the one to successfully challenge the dragon, and concentrated all of his time and attention on this pupil. When Danny became the Iron Fist, K'un L'un's disposition changed dramatically. Master Khan, angered at the death of his dragon, demanded Iron Fist as a blood sacrifice. Lei Kung's intervention saved Danny's life. After Danny was imprisoned by the H'ylthri, Lei Kung was among those who helped free him. When Davos stole the Iron Fist and returned to K'un L'un, the Thunderer brought Danny into the city to defeat the Steel Serpent, knowing that only the true Iron Fist could prevent his son from becoming a tyrant.
The Thunderer can be found in K'un L'un training the next generation of immortals and waiting for his son, Davos, to reform and return.