The Emperor of Hell, also known as the “Emperor of the Northern Yin of Fengdu”, is the supreme deity of the Taoist underworld. The belief in the Emperor of Hell originated at an early date. The Classic of Mountains and Seas contains a record of the Ghost Realm, saying that there is a large peach tree on Dushuo Mountain, from which flags fly 3,000 li. The branches of the tree point northeast, where the Ghost Gate is located, the place where all the ghosts go in and out. There are two divine beings at the gate, one called Shentu and the other Yulei, who are in charge of leading the ghosts. The Taiping Jing also contains the idea of the underworld summoning people's souls to examine them. The text says: “The great yin law court, calculating the burden they bear, subtracting the years. After the calculation is complete, the local yin god is summoned, along with the earth god, to collect the body and examine the soul.” The Jin Dynasty geomancer Ge Hong's Pillow Book also says: “Zhang Heng and Yang Yun are the northern ghost emperors, ruling over Luofeng Mountain.” In fact, Ge Hong also recorded the “Five Ghosts Emperors” in “The Book of the Original Immortals”: 
It says that the Eastern Ghost Emperor governs Taozhi Mountain, the Southern Ghost Emperor governs Luofu Mountain, the Western Ghost Emperor governs Batang Mountain, the Central Ghost Emperor governs Baodou Mountain, and the Northern Ghost Emperor is Zhang Heng and Yang Yun, who govern Luofeng Mountain. Later, Liang Tao Hongjing depicted “Fengdu Dadi” more systematically in “Zhenling Weiye Tu” and “Zhenhao”. The seventh rank in the “Zhenling Weiye Tu” is Fengdu Beiyin Dadi, and the note says: “Yan Emperor Dading, whose name was Qingjia, is the ancestor of all ghosts and gods in the world. He governs Luofeng Mountain and replaces every 3,000 years.” The Zhenhao says: Luofeng Mountain is in the northern Guidi, and there is the palace of the six deities on the mountain, which is the Six Heavens. The first palace is named Mingzhou Jueyin Heavenly Palace, the second palace is named Haosha Liangshizong Heavenly Palace, the third palace is named Chen'nai Fancheng Heavenly Palace, the fourth palace is named Tianzhao Zuqi Heavenly Palace, the fifth palace is named Zongling Qifei Heavenly Palace, and the sixth palace is named Gansilianwanlv Heavenly Palace. Legend has it that after death, the average person is first received into the first palace, while the holy and virtuous are first received into the third palace in the morning. It is believed that one should do good deeds in life in order to have a good outcome. The above shows that the Daoist Lord of Hell Fengdu lives in Luofeng Mountain in the north, and this belief continued until the end of the Tang Dynasty and the Five Dynasties. In the Song Dynasty, there were new changes in the records about Lord of Hell Fengdu. For example, in Song Dynasty writer Fan Chengda's “Wu Chuan Lu” (Record of Wu Ships), it is written: Fengdu County, Zhongzhou Prefecture, three li from the county seat, is Fengdu Mountain. According to historical records, both Wang Fangping of the Western Han Dynasty and Yin Changsheng of the Later Han Dynasty attained immortality here. There is a furnace where Yin Jun refined immortality pills. Yin Jun refined immortality pills to help people, and his method is still passed down. It can be seen that in the Song Dynasty, people believed that Fengdu Yin Jun was Yin Changsheng, and called Wang Fangping Yin Wang Yin Changsheng. The Qing Dynasty scholar Yu Yue wrote in his book “Cha Xiang Shi Cong Cao”: “Fengdu County's Pingdu Mountain is one of the 72 blessed places in Taoist scriptures, and is suitable for immortals to live in. It is incomprehensible that the world believes it is the abode of the Ghost King. Reading ‘Wu Chuan Lu’ (Record of Wu Ships) reveals that it is due to a miscommunication from the Lord of the Underworld, which has been passed down for a long time. People did not know it was the Immortal Changsheng, and thought it was the Lord of the Underworld. This is where this common saying comes from.” Yu Yue explained the origin of the name “Luofeng Mountain” as follows: “Luofeng Mountain is ruled by the Emperor of Ghosts in the north, hence the saying that Luofeng governs ghosts. The world, however, refers to Fengdu County in Sichuan Province. The Yijian Zhi records: 'There is the Fengdu Temple in Fengdu County, Zhongzhou, and its mountain is called Panlongshan, which is the hell at the North Pole according to Taoism. This saying already existed in the Southern Song Dynasty.” The Qing Dynasty scholar Fang Xiangying's “Diary of a Journey to Sichuan” also says: “Fengdu County is located at the foot of Mount Pingdu, one of the 72 blessed places in Taoist scripture, and is known as the ‘capital of the underworld’.” This shows that the underworld of Fengdu Emperor was moved to Fengdu County in Sichuan during the Song Dynasty. Later, the “Fengdu Temple Poems” says: “There is the court of the Lord of the North Yin in the clouds, and the black book of the Great Yin imprisons the spirits of the dead.” The note says: “According to Taoist priests, this place is where the Lord of the North, Luo Feng, reigns.” Volume 5 of “Yi Jian Zhi Zhi” also says: “There is a Fengdu Temple five li outside Fengdu County in Zhongzhou, which is where Taoists call the northern polar hell.” In short, the belief in the Sichuan Fengdu Hell is still very popular among the common people today.

 酆都大帝又称“酆都北阴大帝”，是道教阴府地狱的最高神灵。酆都大帝信仰起源较早，《山海经》中即有鬼国的记载，称度朔山上有大桃木，出幡三千里，其枝问东北叫鬼门，为万鬼出入的地方，门上有二神人，一叫神荼，一叫郁垒，主阅领万鬼。《太平经》中亦有阴府召人灵魂考人魂魄的说法，文曰：“大阴法曹，计所承负，除算减年。算尽之后，召地阴神，并召土府，收取形骸，考其魂神。”晋葛洪《枕中书》亦云：“张衡杨云为北方鬼帝，治罗酆山。”其实葛洪在《元始上真众仙记》中还记载了“五方鬼帝”， 
文称：东方鬼帝治桃止山，南方鬼帝治罗浮山，西方鬼帝治幡冢山，中央鬼帝治抱犊山；而北方鬼帝为张衡杨云，治罗酆山。后来梁陶弘景在《真灵位业图》和《真诰》中将“酆都大帝”描绘得就较为系统了，《真灵位业图》神阶第七位即为酆都北阴大帝，注云：“炎帝大庭氏，讳庆甲，为天下鬼神之宗，治罗酆山，三千年而一替。”《真诰》中说：罗酆山在北方癸地，山上有六丁鬼神之宫，是为六天。第一宫名明纣绝阴天宫，第二宫名豪煞谅事宗天宫，第三宫名晨耐犯武城天宫，第四宫名恬昭罪气天宫，第五宫名宗灵七非天宫，第六宫名敢司连宛屡天宫。传说一般人初死后都要以第一宫受事，而圣贤之人死去是先到明晨第三宫受事，认为人生在世应多做功德善事，才有好结果。上述表明，道教的酆都大帝住在北方的罗酆山，这种说法一直延续到唐末五代。 　　及至宋代，有关酆都大帝的记载又有了新的变化。如宋范成大《吴船录》载：忠州酆都县，去县三里有酆都山，碑牒所传，西汉王方平后汉阴长生皆在此得道仙去，有阴君丹炉。……阴君以炼丹济人，其法犹传。可见宋时人们认为酆都阴君为阴长生，并称王方平为阴王阴长生为阴君。清人俞樾在《茶香室丛钞》中按日：“酆都县平都山，道书七十二福地之一，宜为神仙窟宅，而世乃传为鬼伯所居，殊不可解。读《吴船录》乃知因阴君传讹，盖相沿既久，不知为阴长生，而以为幽冥之主者，此俗说所由来也。”在解释“罗酆山”时，俞樾说：“按罗酆山为北方鬼帝所治，故有罗酆治鬼之说，而世俗乃指今四川酆都县。《夷坚志》云：‘忠州酆都县有酆都观，其山曰盘龙山，即道家所称北极地狱之所。’盖南宋已有此说。”清人方象瑛《使蜀日记》亦曰：“酆都县城倚平都山，道书七十二福地之一，素以‘鬼国都城’闻名。”由此可见，宋时酆都大帝的地府迁到了四川酆都县。后有《酆都观诗》曰：“云有北阴神帝庭，太阴黑簿囚鬼灵。”注曰：“道士云，此地即谓北都罗酆所主。”《夷坚支志》卷五亦云：“忠州酆都县五里外有酆都观，即道家所称北极地狱之所。”总之四川酆都地府之说至今在民间仍然信仰非常兴盛。