The four great immortals, namely Zhang Tian Shi Zhang Daoling, Xu Tian Shi Xu Xun, Sa Tian Shi Sa Shoujian, and Ge Tian Shi Ge Xuan, are revered in Taoism as the four great immortals.
Zhang Tian Shi is Zhang Daoling, the founder of Taoism, also known as “the Supreme Lord of the Tao of Suppressing Demons and Protecting the Way”, “the Great Emperor of High Wisdom”, “the True One of the Real”, and “the Ancestral Immortal”.
Zhang Daoling's original name was Zhang Ling (34-157), courtesy name Fuhan, and pseudonym Tianshi, and he is revered in Taoism as Zhang Daoling. He founded the Wudoumi Dao at the end of the Eastern Han Dynasty and was later revered by Taoism as its founder. Zhengyi Zhenren was the title bestowed upon him by the Supreme Lord. The Qingwei Immortal Genealogy, the General History of Immortals and the Biographies of Immortals all record that he was the eighth-generation descendant of Zhang Liang, the Han Dynasty strategist, and a native of Peiguo (present-day Feng County, Jiangsu Province). His father, Zhang Yi, courtesy name Taishun, once lived as a guest in Tianmu Mountain. His mother became pregnant after dreaming one night that the Great Dipper's Kui Star descended and bestowed on her the herb Herba Erigeron. After returning to Pei, he was born on the first day of the fifth lunar month (May 18) during the Jianwu period (25–56). 
At the time of his birth, the room was filled with yellow clouds and purple vapour, and there was a light in the sky like an egg. Zhang Daoling was bright and intelligent from an early age. When he was seven years old, he met the Master He Shang, who taught him the “Tao Te Ching” and enabled him to understand the subtle meaning of the 5,000 words. As an adult, he had a strange appearance: he was 9 feet 2 inches tall, with bushy eyebrows, a broad forehead, a red crown and green eyes, a high forehead and square jaws, and two horns on his eyes. He was well-versed in the Four Books and Five Classics, and knew astronomy, geography, and the books on the Lo and He diagrams. He attended the Imperial University and studied various classics. At the age of 26, he was selected for the “Excellent and Virtuous Scholar” exam. During the reign of Emperor Ming of the Eastern Han Dynasty (58-76), he served as magistrate of Jiangshan in Ba County (present-day Chongqing). Later, he retreated to the Mount Beimang (present-day Beimangshan in Luoyang, Henan Province) to cultivate immortality. It is said that Wei Boyang once took him as a disciple and imparted his secrets. The imperial court summoned him as a doctor, but he claimed illness and did not go. Emperor He (89-105) summoned him as a tutor and bestowed upon him the title of Marquis of Jixian, but he declined the appointment three times, preferring to pursue his spiritual practice. He obtained the Yellow Emperor's Nine Cauldrons Elixir through sincere cultivation. Later, he took his disciples to Yunjin Mountain to cultivate the Way of the Mysterious and the Mysterious, and refine the Great Dragon and Tiger Elixir. He also lived on Songshan Mountain, meditating and contemplating, and obtained the “Internal Writings of the Three Emperors” and “Nine Cauldrons Elixir Scripture of the Great Qing”. He then travelled to famous mountains to seek the Way and cultivate himself. During the reign of Emperor Shun (126-144), he was attracted to Sichuan for its simple folk customs and the beautiful mountains, valleys, streams and waterfalls. He entered Sichuan and, on Heming Mountain (also known as Que Ming Mountain, in the territory of present-day Dayi County, Sichuan), refined the Divine Elixir of the Nine Cauldrons for three years. After taking the pill, he returned to youth, so he continued to travel west to explore the source of immortality and obtained the secret text of the sacred tortoise that summoned all spirits in the five mountains. He practiced diligently and cultivated his skills to the point where his magic was boundless and unfathomable to the world. According to “The Complete Biography of Immortals,” Zhang Ling was adept at using talismanic water to cure diseases, and his achievements gradually became known. Later, he obtained the Secret Script of the Supreme Alliance of the Supreme Lord, the Three Pure Ones Sutras, the Secret Script of Talismans and Alchemy, the Seal Sword, the Dharma Robes, etc. He worshipped and governed the eight ghosts and gods in Shu, the six heavenly kings, and ordered the five parties, eight parties, and six heavenly gods to meet at the Yellow Emperor Altar on Qingcheng Mountain, so that humans and ghosts could be governed separately, and the prison of ghosts and gods could be turned into the Twenty-Four Blessing Halls. This is the 24 divisions of governance, each with a yin official and a xian official in charge of human affairs and blessings and misfortunes respectively. Later, he went to Yuntai Mountain in Cangxi County to cultivate the merit of nine returns and seven returns in preparation for ascending to heaven, but because he had killed too many ghosts, he was ultimately unsuccessful. Taishang Laojun then let him cultivate his gratitude and remain on earth. He then returned to Heming Mountain, wrote 24 Daoist books, and founded the Wudoumi Dao, also known in later generations as Tianshi Dao and Zhengyi Dao. Later, he led his disciples on a journey to various mountains to practice and repent. His efforts were successful, and Taishang Laojun led Zhang Ling to ascend to heaven, where he worshipped Yuanshi Tianzun and was appointed Zhengyi Pinge Dafashi. He was told to return to the mortal world to preach to those who had not yet awakened to the Dao, so he descended to earth to perform rituals and exorcise demons. He became the Heavenly Master who exorcises demons and wards off evil spirits. Once he is in the right state of mind, the demons are instantly banished. In the second year of Yongshou (155-158) (156), after his achievements were well-known and his Daoist teachings were well-received, he was greeted by the gods and ascended to heaven in broad daylight.
Since then, Zhang Ling's descendants have inherited the Tianshi Dao law and have been given titles by the imperial court in successive generations: in the sixth year (747) of the Tang Tianbao period (742-756), the Tianshi was conferred the title of “Taishi”; Tang Xizong conferred the title of “Santian Fujiao Fuyuan Dafashi” on the Tianshi; Song Lizong conferred the title of the “Great Master of the Three Heavens, the One Who Supports the Dao and Assists the Yuan, the One Who Is Silent and Answers, the True Lord Who Bestows Mercy”; the Yuan Emperor Chengzong additionally conferred the title of “True Lord of the One Who Charges Forward, the Original Spirit Who Transforms, the One Who Is Silent and Answers, the True Lord Who Bestows Mercy”; and in the first year of the Ming Emperor Gongwu's reign (1368), the title was changed to “True Person”.
The name “Tianshi” is first mentioned in the text “Zhuangzi: Xu Wugui”: “The Yellow Emperor bowed again and again, called Tianshi, and then withdrew.” It actually refers to a respectful term, but the name Tianshi originated from this. Li Ying's Shu Ji (Records of Shu) states that Zhang Ling entered Heming Mountain and called himself Tianshi. There were also Kou Tianshi (Qian Zhi) of the Northern Wei Dynasty, Lu Tianshi (Xiujing) of the Liu Song Dynasty, Du Tianshi (Guangting) of the Tang Dynasty, Sa Tianshi (Shoujian) of the Song Dynasty, etc. The title “Tianshi” was first used to refer to Zhang Daoling, and it was first mentioned in the Jin Shu (History of the Jin Dynasty) in the biography of Hao Chao. The biography says, “Yin followed the Tianshi Dao, while Chao worshipped the Buddha.” Zhang Daoling's Dao was thus called Tianshi Dao. Although the Ming court did not use the title Tianshi, people in later generations still called him Tianshi, and this has continued to the present day.
Zhang Daoling is the founder of Taoism, and because he was highly skilled in Taoist practices, could subdue demons and evil spirits, and had great supernatural powers, he was able to ascend to immortality in broad daylight. He is also depicted in stories about immortals from past dynasties, and his influence in the folk religion has been significant, and he is still worshipped today.
Xu Tianshi was Xu Xun, a Taoist priest from the Jin dynasty, courtesy name Jingzhi, from Nanchang (present-day Jiangxi), also known as Xu Zhenjun. According to the Twelve True Gods Biography: “Xu Zhenjun's name was Xun, his style name was Jingzhi, and he was originally from Runan. His grandfather Yan and father Su followed the Daoist path from generation to generation.” The Complete Collection of the Origins of the Three Religions and the Teachings of the Gods records that Xu Xun was born on the 28th day of the first month of the second year of Wu Chiwu (238-251) (239). His mother had a dream in which a golden wind carried a pearl into her arms, and she conceived and gave birth. In his early adulthood, he studied under Wu Meng, a Daoist immortal, and received the teachings of the Three Primes. He was well-versed in history and the classics, astronomy and geography, the calendar, the five elements, and books on divination and astrology. He was even more interested in the cultivation of immortals. According to the Records of the Seven Oracles of the Clouds, Xu Xun was once hunting and shot a pregnant doe. In due course, the doe gave birth to a fawn. The doe that had been shot, despite everything, turned back and sadly licked the fawn. Xu Xun was very sad when he saw this, and with a sense of forlornness, he broke his bow and arrows and was determined to follow the path of immortals. In the first year of the Tai Kang reign (280-290) of the Jin Dynasty (280), Xu Xun was selected as a filial and honest official at the age of 42 and was appointed magistrate of Jingyang County in Shu. During his political career, he was just and honest, and the officials and people were obedient. The people felt his kindness and built a shrine to worship his image. People affectionately called him Xu Jingyang. Later, during the chaos of the Jin dynasty, he even abandoned his official post and returned to the east, wandering the rivers and lakes in search of the Way. During this time, he travelled with Wu Jun to the left side of the Yangtze River, and together with Guo Pu, they secretly stopped the Wudun rebellion. After Guo Pu was executed by the Wudun, he and Wu Jun once again went into hiding, and when they reached the mouth of the Lujiang River, they met a boatman and converted him, teaching him to take herbs and imparting to him the techniques of immortals. Later, he met Shengzhen, who taught him the Taishang Lingbao Jingming Method, which taught him how to slay demons and capture evil spirits. Soon after, he travelled to Yuzhang and met a young man named Shenlang, who was transformed by a sea serpent spirit. The sea serpent spirit had repeatedly caused floods in Jiangxi, so Xu Xun transformed into a black ox and led his disciples to kill it, thus eliminating the water disaster in Jiangxi. Since then, Xu Xun's Daoist methods have become widely known, and his reputation has spread far and wide. Many people sought to become his disciples.
In the second year of the Ning Kang period (373-376) of the Eastern Jin Dynasty (374), he and his family flew up in the sky during the day from Xishan in Yuzhang (now Xishan in Nanchang, Jiangxi). The villagers and his clan members built a shrine to worship him. One hundred and twenty of his poems were engraved on bamboo slips for people to consult to determine their fortunes. The name of this divination method was “sacred slips”. In the second year (1112) of the Zhenghe reign (1111–1118) of the Northern Song emperor Huizong, he was posthumously honoured as “Shen Gong Miao Ji Zhen Jun” (literally “Divine Lord of Miraculous Salvation”) because the emperor had been cured of an illness in a dream by Xu Xun. The temple was upgraded to a palace and given the name “Yulong Wanshou Gong” (Palace of Eternal Youth on the Jade Dragon Mountain) (the palace is located on Xishan in present-day Nanchang, Jiangxi). During the Southern Song Dynasty in Shaoxing (1131-1163), it is said that the Taoist priest He Zhen Gong of the Yulong Wanshou Palace in Xishan prayed to Xu Zhenjun to descend and save the war-torn land, and was granted the Flying Immortal's Sutra of Salvation and the Great Dharma of Purity, Wisdom, Loyalty and Filial Piety by Xu Xun. During the Yuan Dynasty, Taoist priest Liu Yu used “Purity and Wisdom” as the name of his sect, with its main scripture being the Complete Collection of the Purity and Wisdom Loyalty Teachings, and Xu Xun was worshipped as the sect's founder, establishing the “Purity and Wisdom Loyalty and Filial Piety Dao”. Later, Taoism regarded him as one of the four great immortals, along with Zhang Daoling, Sa Shoujian, and Ge Xuan.
Sa Shoujian, also known as Sa Zhenren, Chong'en Zhenjun, was said to be the famous Taoist priest Sa Shoujian of the Song Dynasty, also known as Quanyangzi. One theory is that he was from Xihe in Shu (now Xichongning County, Sichuan), while another is that he was from Nanhua (now Nanhua County, Qujiang County, Guangdong). Zhao Daoyi of the Yuan Dynasty's “A General History of the Daoist Immortals” says: “He called himself Fenyang Sa Ke.”
When he was young, Sa Shoujian was a doctor. Because his medical skills were not very good, he prescribed the wrong medicine and killed someone, so he gave up medicine and followed the Dao. He studied under the 30th-generation Tianshi Master Xu Jing, Lin Lingsu, and Wang Zhichen. According to the records in the second volume of “The Complete Collection of the Gods of the Three Religions”, the eighth volume of “The Complete Biography of the Immortals” and the twentieth volume of “The Complete History of the Immortals”, Mr. Xu Jing passed on his secret art of enchanted dates, Wang Shichen passed on his thunder method, and Lin Lingsu passed on a magic fan. After learning the secret arts, Sa Shoujian used the enchanted dates to relieve the suffering of the poor, the thunder method to eliminate evil and harm, and the magic fan to avenge the people. His Taoist skills were thus widely known and highly regarded. He was later known as Chong'en Zhenjun and was also bestowed the title of Tianzhulingwei Zhenren by the Jade Emperor.
Legend has it that Sa Shoujian used his magic to summon the Jade Pivot Fire Palace Heavenly General Wang Lingguan, who became his subordinate and passed on the secrets of his talismans. However, Wang Lingguan's reputation far surpassed that of his master among the common people. During the Yongle reign (1403–1425) of the Ming dynasty, the temples dedicated to Wang Lingguan and Sa Shoujian were extremely popular. In Taoism, he is one of the four great immortals, along with Zhang Daoling, Ge Xuan, and Xu Xun.
The Tianshi's surname was Ge, his name was Xuan, and his style name was Xiaoxian. He was from Jurong in Danyang (now Jurong City in Jiangsu Province). According to the Baopuzi, he was a Daoist alchemist in the Three Kingdoms period who studied Daoism from Zuo Ci, practiced Daoist techniques, and received the Nine Cauldrons of the Daoist Scripture, the Supreme Daoist Scripture, the Scripture of the Golden Elixir, and other secrets. It is said that he practiced Taoism on Zuozishan Mountain in Jiangxi Province, often fasting and taking elixirs, and was adept at charms and spells, able to use talismans to drive away illness and evil for others. Taoism reveres him as “Ge Xian Gong” and also calls him “Taiji Zuo Xian Gong”. Liang Taojing's “Zhenling Weiye Tu” ranks him third.
There are many legends about him in Taoism and folklore. Some say that he could turn the rice grains he spat out into thousands of bees, make stubborn stones walk, and make toads, insects, and sparrows dance to the five notes and six rhythms under his command. He could also draw talismans to pray for rain for the people, some say that he could catch demons and once whipped a demon in a hotel, relieved a scholar of a snake under the command of the conductor, dancing to the tune of the pentatonic scale, he could draw talismans to pray for rain for the people. Some say that he could catch demons and once whipped a demon at a hotel, relieved a scholar of a snake
spirit, burnt an evil temple and a small evil spirit. Some say that he once went out with Sun Quan and sank in the river for several weeks before returning. Some say that he once gave the two daughters of the Qu family elixirs, which made them immortal after taking them. Some say that he once refined food and medicine on a stone wall and accidentally dropped a pill, which was eaten by a bird and turned it into a crane. Some say that after his meritorious deeds were complete, the Eastern Emperor of the Heavens recorded his name in the immortal register. In short, his immortal deeds were very extensive.
In the third year of the Chongning reign (1104) of the Song Dynasty (1102–1107), he was conferred the title of “True Immortal of the Great Response”, and in the third year of the Chun reign (1243) of the Southern Song Dynasty (1241–1253), he was conferred the title of “True Immortal of the Great Response and Faithful Lord”. In Taoism, he is one of the four great immortals, along with Zhang Daoling, Xu Xun and Sa Shoujian.