Trial of Shou-Lao

"Hey, why don't you tell me again about how you punched the dragon and got your magic hand?" "During the final trial of Shou-Lao the Undying, I plunged my fist into his molten heart."

- Luke Cage and Iron Fist

The Trial of Shou-Lao was a successfull attempt by Danny Rand to defeat Shou-Lao the Undying and become defender of K'un-Lun known as "Iron Fist".

Background
During Danny Rand's time as a student in K'un-Lun, he learned of the position of the Iron Fist, a title of great power and importance throughout the realm. Rand grew ambitious and set out to make himself worthy of gaining the power of the Iron Fist, competing with several other students to reach his goal. Despite many believing that his being an outsider made him incapable of earning the title, Rand's determination grew further.

Trial
Many years later, Rand was indeed given the opportunity to gain the power of the Iron Fist. He was sent to battle the enormous fire-breathing serpent called Shou-Lao the Undying which lived in a Cave outside the city. It ferociously guarded a brazier containing its heart, which had mystically been removed from its body. In their battle, Rand grabbed the serpent's body, which bore a scar that imprinted itself upon Rand's chest. Rand plunged his hands into the now unguarded brazier containing Shou-Lao's molten heart when his hands shone with a quasi-mystical force and he earned the title "Iron Fist," for he could now summon superhuman energy to reinforce the power of blows struck by his hands.

Aftermath
"It was not like I imagined it." "It is never how you imagined it."

- Danny Rand and Davos

After succeeding in his trial, gaining his powers and the Mark of Shou-Lao onto his chest, Rand was left unconscious outside the cave. He was eventually found by Davos who woke him up. When his friend rushed at him, Rand woke up and summoned his Iron Fist. Astonished, Davos told Rand that he succeeded in his trial.

Several years later, Rand escaped from K'un-Lun and used his power to fight againist Hand.