The immortal being Monkey, called Sun Hou-Tzu by the Chinese, is undoubtably one of the most popular characters in Chinese folklore.
No ordinary mammal, Monkey was hatched from an egg. His birthplace was a land on the eastern side of the Pacific. That makes him a New World monkey and so probably has a very useful prehensile tail. In spite of being an animal, Monkey's intelligence was considerable and he impressed a great Taoist (Daoist) Immortal. The Immortal taught Monkey powerful magic but Monkey's morality did not match his intelligence. He selfishly used his magic to become the ruler of all of the monkeys in the world.
Ruling monkeys was not enough for the ambitious Monkey, however. A Dragon King gave Monkey a magical weapon but instead of just using it to defend his monkey subjects, he tried to conquer the whole world. Rice wine is not very alcoholic but fortunately for both humanity and Heaven, Monkey was tricked into drinking so much that he became incapacitated. Monkey's dreams of world conquest being foiled, his divine enemies were able to send him to the Chinese concept of Hell, Diyu, as punishment for his megalomaniac crimes. However, Monkey escaped from Diyu. Before leaving, though, he did his monkey subjects a good turn by deleting all of their names from the Book of Judgments.
The Lord of Heaven, Jade Yu-Ti, decided that Monkey's mischief may have been the result of idleness and made a big show of giving Monkey the very important position of Master of Heaven's Stables. When Monkey learned the real reason for his appointment, however, he became incensed and wrought havoc in Heaven.
The Lord of Heaven was forced to send his armies to recapture Monkey but Monkey took refuge on Mount Hua-Kuo. There he defeated the Heavenly armies. He proclaimed himself to be a saint and declared that he was now Lord of Heaven.
The real Lord of Heaven had the patience of a saint Himself and decided to make peace with Monkey. He gave Monkey an even more important appointment, putting him in charge of the Heavenly Peach Orchard of Immortality. Perhaps predictably with the benefit of hindsight, Monkey ate the peaches himself. He became immortal. Even though he was now Master of the Heavenly Peach Orchard and an immortal himself, Monkey still exhibited his petty nature. The organisers of the Peach Festival thought that Monkey was in such an exalted position that he would not deign to attend, so they did not invite him. Monkey, however, interpreted this as a slight and took revenge by eating and drinking all of the food and beverages at the festival.
Monkey learned that the Taoist master and alchemist Lao Chun had created pills which bestowed immortality. In spite of already being immortal as a result of eating the Heavenly peaches, Monkey stole the pills. This made Monkey doubly immortal, completely invulnerable to either violence or ageing.
Jade Yu-Ti, the Lord of Heaven, was of course angry at Monkey's recalcitrant behaviour and once again set his followers the task of capturing the errant creature. They succeeded and by this time, the Lord of Heaven had run out of patience and mercy when it came to Monkey. He sentenced Monkey to death. How, though, could he be destroyed, having eaten both the Peaches of Immortality and Lao Chun's immortality pills? Lao Chun was given the task of dissolving Monkey in his alchemical furnace but even that could not harm the now indestructible primate. Monkey just laughed and escaped to continue his destructive rampage.
The Lord of Heaven asked Buddha for help and advice. Buddha realised that even if Monkey could not be killed, he might at least be contained. Buddha offered Heaven itself to Monkey but with a proviso. Monkey must first prove his power by escaping from Buddha's palm. Monkey's conceit and megalomania were such that he accepted the challenge. However, Buddha's command of space and time was such that his palm encompassed the entire Universe. Nobody, not even Monkey, could escape from that. Buddha then imprisoned Monkey in a magical mountain.
The Chinese epic of Hsi Yu Chi, the Journey to the West, (or Journey to the Western Paradise), was inspired by a real event but during the Ming dynasty, the author Wu Cheng'en turned it into a fantastic adventure. In his version of the story, Monkey the mischievious megalomaniac and Pig the glutton redeemed themselves by assisting their holy master in his quest to find the true teachings of Buddha and return them to China.
The true events concern Xuanzang's Journey to the West. In a journey lasting seventeen years, during the Tang dynasty, the Buddhist monk Xuanzang travelled all over the Indian subcontinent, studying the practices of Buddhism there and acquiring many sacred texts before returning to China. Xuanzang's name is sometimes transcribed as Tang Sanzang, Thang Seng or Tang Seng. I shall use the last variant when referring to the fictional events.
Monkey was released from his magical mountain prison, to accompany Tang Seng, and his assistant Pig, on their pilgrimage and quest to the Western Paradise, to bring back the original teachings of Buddha. During their journey, Monkey was forced to wear a magical helmet that painfully contracted at Tang Seng's command. With it, Tang Seng was able to discipline Monkey when he was mischievious or disobedient. In spite of sometimes causing problems by succumbing to their many faults along the way, Monkey and Pig proved to be of great help in the quest. After a successful conclusion to their many adventures, Monkey asked Tang Seng to remove the helmet. Monkey's request was unnecessary, however, as it had already disappeared as a result of his reformation and Buddhist enlightenment.