Lu Dong Bin 呂洞賓(Lü Tung-Pin) is the most famous of the Eight Daoist Immortals. A person both real and legendary, he influenced many Daoist traditions that come down to us today, particularly the Nei Dan (Inner Alchemy) traditions.
Lu Dong Bin 呂洞賓(Lü Tung-Pin) is the most famous of the Eight Daoist Immortals. Born in the Tang Dynasty, he was later elevated to the status of an Immortal. Lu was a historical figure. He is also known as Lü Yan (呂巖). Dong Bin is his courtesy name. “Lü Dong Bin” means the “Host of the Caverns” or “Lu the Cavern Guest.” He is sometimes called Master Pure-Yang (純陽子 Chun Yang Zi), and he is also called Lü the Progenitor (呂祖 Lü Zu) by some Daoists, especially those of the Quanzhen school. 
There are many stories about Lu Dong Bin. One story says that Lu twice failed the top-level exams to become an official (See The Eight Immortals of Daoism Part 2). Before his third attempt he met Zhong Li Quan and this meeting led to his decision to follow the Daoist path. In another series of stories story Lü had to pass 10 tests given to him by Zhong Li Quan ten times before Quan accepted him as a disciple. 
The First Test: After returning home from a long journey, Lü discovered that all of his beloved family members had died. As he prepared for the funeral, showing neither remorse for having been away, nor sadness over the deaths, the family members suddenly all returned to life.
The Second Test: When selling goods in a market, a customer gave Lü only half the money he had agreed to pay, yet took all of the goods. Lü did not get angry or argue but simply let the issue go.
The Third Test: Lü gave some money to a beggar who became greedy and not only demanded more money, but began to swear at Lü. Lü merely responded with a smile.
The Fourth Test: Posing as a shepherd, Lü offered himself to be eaten by a hungry tiger in order to protect his herd of sheep. The tiger left without harming Lü.
The Fifth Test: Lü was staying ina a small mountain hut, when a beautiful woman who was lost on the mountain arrived and came by and asked if she could stay there for the night. In the night, woman made several advances towards Lü beautiful lady but Lü was untouched by temptation.
The Sixth Test: Lü returned to his house to find his possessions had been stolen. Undisturbed by the robbery he began working in the field and immediately found some gold bars. He simply ignored them and reburied them
The Seventh Test: Lü bought some copper or bronze utensils at the market. Upon returning home he discovered they were actually made of gold. He returned them to the seller.
The Eighth Test: Q crazy Daoist was selling medicine on the street. The Daoist said that if consumed, the medicine would cause immediate death, but that in the next lifetime the person taking the medicine would attain enlightenment. Lü drank the potion and was unharmed.
The Ninth Test: Lü was travelling on a river in a boat. A sudden storm came up and the boat was in danger of capsizing. The other passengers were terrified, but Lü was unperturbed and calmly rode out the storm.
The Tenth Test: Ghosts and monsters suddenly appeared in the room where Lü was meditating, yet Lü remained unmoved. Other malevolent spirits appeared and threatened to kill Lü as revenge for his past transgressions. Lü calmly prepared for death and suddenly the spirits disappeared and Lü’s master Zhang Li Quan appeared and told him he was now ready to follow the Dao
Zhang Li Quan is interesting figure who seems to reappear at widely different time periods. He supposedly lived under the Hans, was active under the Jin in the fourth century and appeared many times to famous masters of the Tang and Song dynasties, including Lü Dong Bin. 
Zhang Li Quan purportedly taught Lü Dong Bin inner alchemy and Lü went on to become a patriarch of the inner alchemy schools, including the Northern and Southern schools of “Complete Reality” or “Perfect Realization” Daoism (Quanzhen 全眞 – Literally “Complete True”). Quanzhen was founded in the Song Dynasty (1127–1279) by Wang Zhe, a Nei Dan practitioner whose practice was said to be guided by the Immortals Zhang Li Quan, Lü Dong Bin and Liu Hai Chan. As “Ancester Lü”, Lü Dong Bin is the ancestor of “Zhang-Lü Tradition” of which the Complete Reality School is branch. In the Song Dynasty, Lü’s status as a patriarch of Daoism and as one of the Eight Immortal led to him being viewed in a variety of ways:
Different worshippers saw him as an itinerant religious specialist, a patriarch for the Perfect Realization Taoist movement, a healer and wonder-worker, a patron god of various tradespeople ranging from ink makers to prostitutes, a powerful deity of spirit-writing sects and a member of the that powerful yet rambunctious group of spirits known as the Eight Immortals. These multiple images of Lu were created over centuries by people form many different social groups of later imperial China, including scholar-officials, Taoist priests, dramatists, tradespeople and artisans. 
By the 12th century Lü became the object of a cult, largely due to his purported ability to perform miracles. Many of those involved in the cult of Lü Dong Bin were from the underprivileged classes – prostitutes, itinerant Daoists, hebs sellers, ink-sellers and peddlers. Veneration by these groups led to Lü’s name being used to voice criticism in times of social unrest. 
Many Daoist texts are attributed Lü Dong Bin. One of the main Daoist texts of the Zhang-Lü tradition is the Ling Bao Bi Fai (Complete Methods of the Numinous Treasure), a manual of longevity techniques, which lays out many of the foundational practices of Nei Dan. Another important text, which has been translated by Eva Wong is called Transmission of the Dao Zhong Li Quan and Lü Dong Bin (鍾呂傳道集 Zhong Lü Chuan Dao Ji).  This text, believed to have been written as an introduction to the Ling Bao Bi Fai, employs the device of a conversation between Zhong Li Quan and Lü Dong Bin to present theories and methods of health, longevity and inner alchemy.
Lü was also prolific poet, his works were collected in the Quan Tang Shi (Complete Tang Poetry) and, according to Richard Wilhelm, Lü was the originator of the material presented in the Secret of the Golden Flower (Tai Yi Jin Hua Zong Zhi 太一金華宗旨). According to Daoist legend, Lü is the founder of the internal martial arts style called “Eight Immortals Sword” (八仙剑), considered to be one of the martial treasures of Wudang Mountain. Hence Lü is sometimes referred to as the “Sword Immortal.” He is also sometimes called the “Wine Immortal.”
Lü is associated with many sites in China. A Depiction of Lü appears with Zong Li Quan in the Hall of Purified Yang (Chun Yang Dian) at the Temple of Eternal Joy (Yong Le Gong), a Quanzhen Daoist temple in Southern Shanxi. Lü is also said to have frequently visited Yueyang Tower, overlooking Lake Dongting in Hunan Province, to drink wine. The association of Lü Dong Bin and with the Yue Yang Tower became more widespread with the publication of the play Lü Dong Bin Thrice Intoxicated at Yueyang Tower. A famous poem attributed to Lü mentions Yueyang and Lake Dongting:
In the morning I travel to the North Sea, in the evening to Cangwu,
I my sleeve is a blue-green snake [Lü’s magic sword],
Courageous and rough [is my appearance].
Trice I entered Yueyang, but no one recognized me.
Sing a Song as I flew by lake Dongting. 
 Wikipedia: https://en.wikipedia.org/wiki/L%C3%BC_Dongbin
 Various versions of the Trials of Lü Dong Bin can be found:
1)Wikipedia (See Note #1)
2) Lü Dongbin: His 10 Trials and the ‘Yellow Millet Dream.’ David Wu, http://printarchive.epochtimes.com/a1/en/hk/nnn/2014/10-Oct/30/B5.pdf
3) The Ten Trials of Patriarch Lu Dongbin 十试吕祖© Heavenly Horse Peak Publications 2015. A PDF of Lü Dong Bin’s ten trials before he reached the Dao can be downloaded from the following page:
 Taoism Growth of a Religion. Isabelle Robinet. Translated by Phyllis Brooks (Stanford: Stanford University Press1997) p. 222
 Images of the Immortal: The Cult of Lu Dong Bin at the Palace of Eternal Joy, Paul R. Katz (Honolulu: University of Hawai’i Press, 1999) p. 7.
 The Routledge Encyclopedia of Daoism volume 1: A-L. edited by Fabrizio Pregadio (Londen & New York) Routledge 2008) p. 713.